' 



















s 



THE CHEMISTRY 



OF 



PLANT AND ANIMAL LIFE 



?&&&• 



THE MACMILLAN COMPANY 

NEW YORK • BOSTON • CHICAGO • DALLAS 
ATLANTA • SAN FRANCISCO 

MACMILLAN & CO., Limited 

LONDON • BOMBAY • CALCUTTA 
MELBOURNE 

THE MACMILLAN CO. OF CANADA, Ltd. 

TORONTO 



THE CHEMISTRY 



OF 



PLANT AND ANIMAL LIFE 



BY 

HARRY SNYDER, B.S. 



THIRD REVISED EDITION 



Neto gorfe 

THE MACMILLAN COMPANY 

1913 

All rights reserved 






Copyright, 1903, 
By HARRY SNYDER. 



Copyright, 1903 and 1913, 
By THE MACMILLAN COMPANY. 



First published elsewhere. 

New edition set up and electrotyped. Published December, 1903. Reprinted 
December, 1905; October, 1907; January, 1909. 
Third revised edition, September, 1913. 



Nortoooti ^rfgg 

J. S. Cushing Co. — Berwick & Smith Co. 

Norwood, Mass., U.S.A. 



>CI.A35410.* 



PREFACE TO FIRST EDITION 

This book is the outgrowth of instruction in chem- 
istry given in the School of Agriculture of the Univer- 
sity of Minnesota. At first the classes were small, 
and individual work with blackboard exercises and ref- 
erences to the literature in the school library was possible. 
With increased number of students, mimeographed notes 
were supplied, until finally the size of the classes and the 
volume of the notes have necessitated their publication 
in book form. The work was first given, in 1 891, to a class 
of seven students, while in 1903 they numbered 150. 

The students to whom this instruction has been given 
have been mostly earnest workers who attended school 
mainly from personal choice and who desired to make 
as much progress as possible. Numerous questions have 
been asked by them relating to the application of chemistry 
to farm and everyday life, and for a number of years 
the author kept a box in which were placed the more 
important of these questions together with notes of the 
difficulties experienced in the laboratory : and in develop- 
ing the work from year to year these questions and diffi- 
culties have been considered. 

This work was originally outlined as Agricultural 
Chemistry, but as special features have been developed 
and published, as "Soils and Fertilizers," and "The 
Chemistry of Dairying," this part of the subject has 
gradually developed into " The Chemistry of Plant and 
Animal Life," and includes the composition of plant and 



VI PREFACE TO FIRST EDITION 

animal bodies, the chemistry of the plant and of its food 
and growth, the chemistry of human foods and animal 
nutrition, the digestibility and value of foods and the laws 
governing their economic use. A few topics of an in- 
dustrial nature but closely related to plant and animal 
life are also included. 

Before taking up the parts relating to the chemistry 
of plant and animal bodies, the elements and the simpler 
compounds present in plants and animals, together with 
the laws governing their combinations, are considered so 
as to prepare the way for a more intelligent study of the 
subject, and to show the relation which exists between 
chemistry and plant and animal life. Laboratory practice 
forms an important feature, and questions are asked in 
connection with each experiment. Many of the experi- 
ments and problems are given to illustrate some special 
phase of the composition of plant and animal bodies. 
The illustrations, with the exception of a few as noted, 
are original. 

It has been the aim throughout to present the topics 

in such a way that they would be easily understood and to 

develop the reasoning powers of the student so that he 

would be able to make the best use of his chemistry in 

everyday life affairs. 

HARRY SNYDER. 

St. Anthony Park, St. Paul, Minn. 

First edition, March i, 1903. 
Second edition, Nov. 11, 1903. 



PREFACE TO' REVISED EDITION 

In revising this work it has been the aim to retain the 
individuality as expressed in the preface of the first 
edition, with such changes and additions as are in accord 
with recent investigations. 

It has been deemed best to make a sharper division 
between the first part, which deals with the elementary 
principles of chemistry from an agricultural viewpoint, 
and the second part, dealing more distinctively with the 
chemistry of plant and animal life. 

Many colleges in which this subject is taught give more 
extended courses in general chemistry than is presented 
in Part I of this work, in which case the student is already 
prepared, with a special review, to begin Part II. In 
other institutions the time allotted to chemistry is so 
limited as to necessitate a brief course, and then Part I 
or its equivalent should be given before undertaking Part 
II. 

The problems, laboratory practice, and collateral 
reading as suggested, are essentials of the work, and suffi- 
cient time should be allotted in the curriculum, to permit 
a rational study of the subject. It should be the aim 
to master the principles which form the basis of the sub- 
ject so as to intelligently apply them to the solution of the 
new problems which continually present themselves. 

HARRY SNYDER. 
Minneapolis, Minn. 
May, 19 1 3. 

vii 



CONTENTS 

INTRODUCTION 

Chemistry in its relation to plant and animal life ; Relation to 
other sciences ; How to study chemistry ; Reference books and how 
to use them ; Importance of chemistry. Pages xix-xxii. 

PART I 

CHAPTER I 

Composition of Matter. — Physical and chemical changes ; Inde- 
structibility of matter ; Molecules ; Atoms ; Elements ; Com- 
pounds ; Chemical affinity ; Mechanical mixtures ; Chemical anal- 
ysis and synthesis ; Summary. Pages 3-8. 

CHAPTER II 

Properties of Elements and Compounds. — Physical properties ; 
Chemical properties ; Symbols of the elements ; Formulas of com- 
pounds ; Atomic weights ; Molecular weights ; Law of definite pro- 
portion ; Valence ; Combination of elements ; Problems on com- 
bination of elements; Experiments and questions. Pages 9-18. 

CHAPTER III 

Laboratory Manipulation. — Importance of laboratory practice ; 
Names and uses of apparatus ; Cutting glass tubing ; Bending glass 
tubing ; Perforating corks ; Weighing ; Measuring liquids ; Obtain- 
ing reagents from bottles ; Filtering ; Laboratory notebook ; 
Breakage of apparatus ; Care of sinks and plumbing ; How to ac- 
complish the best results in the laboratory. Pages 19-29. 

CHAPTER IV 

Oxygen. — Occurrence ; Preparation ; Properties ; Importance ; 
Problems, experiments, and questions ; Part taken in plant and ani- 
mal life. Pages 30-35. 

ix 



CONTENTS 



CHAPTER V 



Hydrogen. — Occurrence ; Preparation ; Properties ; Impor- 
tance ; Problems, experiments, and questions ; Part taken in plant 
and animal life. Pages 36-40. 



CHAPTER VI 

Nitrogen. — Occurrence ; Preparation ; Properties ; Importance ; 
Problems, experiments, and questions ; Part taken in plant and 
animal life. Pages 41-44. 

CHAPTER VII 

Carbon. — Occurrence ; Preparation ; Properties ; Coal ; Allotro- 
pism ; A reducing agent ; Combustion ; ' Spontaneous combustion ; 
A decolorizer and deodorizer ; Products of combustion ; Com- 
pounds of carbon ; Importance ; Experiments and questions ; Part 
taken in plant and animal life. Pages 45-53. 



CHAPTER VIII 

Water. — Chemical composition ; Physical properties ; Water of 
crystallization ; Natural waters ; Impurities and relation to dis- 
eases ; Location of wells ; Mineral impurities ; Contamination of 
drinking water ; Methods of improving drinking waters ; Water 
filters ; Experiments and questions. Pages 54-62. 



CHAPTER IX 

Air. — A mechanical mixture ; Carbon dioxid ; Ammonium com- 
pounds ; Moisture ; Atmospheric constituents present in small 
amounts ; Liquid air ; Organic impurities and ventilation of rooms ; 
Air, a source of plant food ; Sources of contamination of air ; Ex- 
periments and questions ; Importance of air in plant and animal life. 
Pages 63-68. 



CONTENTS XI 

CHAPTER X 

Acids, Bases, Salts, and Neutralization. — Classification of ele- 
ments ; Acids ; Bases ; Salts ; Radicals ; Naming of acids ; Naming 
of bases ; Naming of salts ; Double salts ; Acid salts ; Basicity of 
acids ; Two series of salts. Pages 69-75. 



CHAPTER XI 

Hydrochloric Acid, Chlorin, and Chlorids. — Occurrence ; Prepara- 
tion ; Properties ; Preparation of chlorin ; Properties ; The chlorin 
group of elements ; Chlorids ; Problems ; Experiments and ques- 
tions. Pages 76-81. 

CHAPTER XII 

Nitric Acid and Nitrogen Compounds. — Occurrence ; Preparation ; 
Properties ; Importance ; Ammonia ; Occurrence ; Preparation ; 
Properties ; Uses ; Oxids of nitrogen ; Anhydrids ; Law of multiple 
proportion ; Utilization of atmospheric nitrogen ; Importance of the 
nitrogen compounds ; Problems ; Experiments and questions. 
Pages 82-88. 

CHAPTER XIII 

Phosphorus and its Compounds. — Occurrence ; Preparation ; 
Properties ; Oxids ; Phosphoric acid and phosphates ; Compounds 
of phosphorus ; Importance of phosphorus and its compounds ; 
Problems; Experiments and questions. Pages 89-91. 

CHAPTER XIV 

Sulfur and its Compounds. — Occurrence ; Preparation ; Proper- 
ties ; Uses ; Sulfur dioxid ; Sulfuric acid ; Properties of H 2 S0 4 ; 
Sulfates ; Sulfids ; Problems ; Experiments and questions. Pages 
92-97. 

CHAPTER XV 

Silicon and its Compounds. — Occurrence ; Preparation and prop- 
erties ; Silicic acid ; Dialysis ; Silicates ; Importance of compounds 
of silicon ; Problems; Experiments and questions. Pages 98-101. 



Xll CONTENTS 

CHAPTER XVI 

Oxids of Carbon, Carbonates, and Carbon Compounds. — Carbon 
dioxid ; Carbon monoxid ; Marsh gas ; Hydrocarbons ; Petroleum ; 
Use of gasoline ; Illuminating gas ; Mineral oils ; Oil of turpentine ; 
Creosote ; Benzene or benzol ; Aliphatic and aromatic series of com- 
pounds ; Carbon disulfid ; Cyanids ; Carbids ; Fuels; B. T. U. value 
of fuels ; Foods ; Production of organic compounds in plants ; De- 
cay of organic compounds; Experiments. Pages 1 02-1 14. 

CHAPTER XVII 

Writing Equations. — Importance ; Common errors in writing 
equations ; Impossible reactions ; A knowledge of reacting com- 
pounds and products necessary ; Equations for classroom work. 
Pages 1 15-120. 

CHAPTER XVIII 

Potassium, Sodium, and their Compounds. — Occurrence of po- 
tassium ; Potassium hydroxid ; Potassium nitrate ; Potassium car- 
bonate ; Potassium chlorate ; Potassium sulfate ; Miscellaneous po- 
tassium salts ; Occurrence of sodium ; Sodium chlorid ; Sodium 
nitrate ; Sodium carbonate ; Sodium hydroxid ; Sodium phosphate ; 
Miscellaneous sodium salts ; Experiments. Pages 1 21-127. 

CHAPTER XIX 

Calcium, Magnesium, and their Compounds. — Occurrence of cal- 
cium ; Calcium carbonate ; Calcium oxid ; Calcium hydroxid ; Cal- 
cium sulfate ; Calcium chlorid ; Bleaching powder ; Calcium phos- 
phate ; Mortar ; Glass ; Occurrence of magnesia ; Magnesium salts ; 
Experiments. Pages 128-132. 

CHAPTER XX 

Iron, Aluminum, and their Compounds. — Occurrence of iron ; 
Reduction of iron ores ; Wrought iron ; Steel ; Rusting of iron ; 
Iron Compounds ; Occurrence of aluminum ; Alums ; Pottery ; Ex- 
periments. Pages 133-140. 



CONTENTS X1U 



CHAPTER XXI 



Copper, Zinc, Lead, Tin, Arsenic, Mercury, their Compounds and 
Alloys. — Commercial importance ; Occurrence of copper and its 
metallurgy ; Copper sulfate ; Bordeaux mixture ; Occurrence of 
zinc ; Compounds of zinc ; Galvanized iron ; Occurrence of tin ; Tin 
salts ; Occurrence of lead ; Oxids of lead ; Lead carbonates ; Lead 
salts ; Uses of lead ; Occurrence of arsenic ; Paris green ; Occur- 
rence of mercury ; Compounds of mercury ; Experiments. Pages 
141-146. 

PART II 

CHAPTER XXII 

The Water Content and Ash of Plants. — Water ; Dry matter ; 
Plant ash ; Form of the ash elements ; Amount of ash in plants ; 
Importance of ash elements ; Water culture ; Sand culture ; Occur- 
rence and function of ash elements ; Potassium ; Sodium ; Calcium ; 
Magnesium ; Aluminum ; Iron ; Phosphorus ; Sulfur ; Silicon ; Chlo- 
rin ; Experiments; Problems. Pages 149-167. 

CHAPTER XXIII 

The Non-nitrogenous Organic Compounds of Plants. — Organic 
matter ; Non-nitrogenous and nitrogenous organic compounds ; 
Classification of non-nitrogenous compounds ; Carbohydrates ; 
General characteristics ; Cellulose ; Occurrence ; Physical proper- 
ties ; Chemical properties ; Function and value ; Food value ; 
Amount of cellulose in plants ; Crude fiber ; Starch ; Occurrence ; 
Physical properties ; Chemical properties ; Function and value ; 
Food value of starch ; Amount of starch in plants ; Dextrin ; Struc- 
tural formulas ; Sugar ; Classification of sugars ; Occurrence of 
sucrose ; Physical and chemical properties of sucrose ; Milk-sugar ; 
Maltose ; Inversion of sucrose ; Refining of sugar ; Occurrence of 
dextrose ; Chemical and physical properties ; Levulose ; Miscel- 
laneous sugars ; Optical properties of sugar ; Sugar-beets ; Food 
value of sugar ; Gums ; Pentosans ; Pectin bodies ; Nitrogen-free 
extract ; Fats ; Presence in plants ; Physical properties ; Chemical 
composition ; Stearin ; Palmitin ; Olein ; Miscellaneous fats ; Sa- 



XIV CONTENTS 

ponification ; Fatty acids ; Waxes ; Food value of fat ; Amount of 
fat in plants and foods ; Ether extract ; Organic acids ; Occurrence 
in plants ; Tartaric acid ; Malic acid ; Succinic acid ; Oxalic acid ; 
Citric acid ; Tannic acid ; Function and food value of the organic 
acids ; Essential oils ; General properties ; Occurrence ; Chemical 
composition and properties ; Essential oils of agricultural crops ; 
Synthetic production of essential oils ; Amount of essential oils in 
plants ; Food value ; Miscellaneous compounds in plants ; Relation- 
ship of non-nitrogenous compounds of plants ; Food value of the 
non-nitrogenous compounds ; Experiments and questions. Pages 
168-203. 

CHAPTER XXIV 

Nitrogenous Organic Compounds of Plants. — Amount of ni- 
trogenous matter in plants ; Different terms applied to nitrog- 
enous compounds ; Complexity of composition ; Classification of 
nitrogenous compounds ; Proteids ; General composition ; Occur- 
rence ; Physical properties ; Chemical properties ; Classification 
of proteids ; Albumins ; Globulins ; Albuminates ; Peptones and 
proteoses ; Insoluble proteids ; Food value of proteids ; Amount in 
plants ; Crude protein ; Albuminoids ; Composition ; Nuclein ; 
Gelatin ; Mucin ; Elastin ; Food value of albuminoids ; Amides and 
amines ; Composition and properties ; Formation and Occurrence 
in plants ; Formation and occurrence of amides in animals ; Food 
value ; Amount in foods ; Protein production and disintegration ; 
Alkaloids ; General composition ; Plant alkaloids ; Animal alka- 
loids ; Food value and production ; Mixed nitrogenous compounds ; 
Lecithin ; Nitrogenous glucosides ; General relationship of the 
nitrogenous organic compounds of foods ; Problems and experi- 
ments. Pages 204-223. 

CHAPTER XXV 

Chemistry of Plant Growth. — Seeds ; Ash ; Non-nitrogenous 
compounds ; Nitrogenous compounds ; Chemical changes during 
germination ; Change of starch to soluble forms ; Change of fats to 
starch ; Change of insoluble proteids to soluble forms ; Germina- 
tion of seeds and digestion of food compared ; Necessary conditions 
for germination ; Heavy- and light-weight seeds ; Movement of 



CONTENTS XV 



plant juices ; Joint action of chemical and physical agents ; Poros- 
ity of tissues ; Osmosis ; Chlorophyl and protoplasm ; Chemical 
action in leaves of plants; Production of chlorophyl; Function; 
Production of organic matter; Experiments. Pages 224-234. 



CHAPTER XXVI 

Composition of Plants at Different Stages of Growth. — Composi- 
tion and stage of growth ; Assimilation of mineral food by the 
wheat plant ; Assimilation of nitrogen by the wheat plant ; Clover ; 
Rapidity of growth ; Flax ; Rapidity of growth ; Maize (corn) ; 
Importance ; Roots ; Stalks ; Leaves ; Tassel ; Husks ; Ripening 
period. Pages 235-244. 

CHAPTER XXVII 

Factors which influence the Composition and Feeding Value of 
Crops. — Seed ; Soil ; Climate ; Stage of maturity ; Method of 
preparation as food ; Improving the feeding value of forage crops. 
Pages 245-249. 

CHAPTER XXVIII 

Composition of Coarse Fodders. — Coarse fodders ; Straw ; 
Timothy hay ; Hay similar to timothy ; Oat hay ; Hay similar to 
oat hay ; Bromus inermis ; Clover hay ; Alfalfa and fodders similar 
to clover ; Rape ; Pasture grass ; Corn fodder and stover ; Silage. 
Pages 250-258. 

CHAPTER XXIX 

Wheat. — Structure of kernel ; Proteids of wheat ; Relation of 
nitrogen in wheat to nitrogen content of flour ; Influence of ferti- 
lizers upon composition of wheat ; Variations in composition of 
wheat ; Storage in elevators ; Manufacture of flour ; Composition of 
unsound wheat ; Composition of different varieties ; American and 
foreign wheats ; Wheat as animal food ; As human food ; Experi- 
ments and questions. Pages 259-272. 



XVI CONTENTS 



CHAPTER XXX 



Maize (Indian Corn). — Structure of the kernel; Composition; 
Proteids ; Nitrogenous and non-nitrogenous corn ; Varieties ; 
Moisture content of corn ; Corn products ; Corn as a food ; Experi- 
ments. Pages 273-278. 

CHAPTER XXXI 

Oats, Barley, Rye, Buckwheat, Rice, and Miscellaneous Seeds. — 

Structure of the oat kernel ; Composition of oats ; Oats as human 
and animal foods ; Barley ; Rye ; Rice ; Buckwheat ; Millet seed ; 
Peas and beans ; Grading of grains ; Experiments. Pages 279-290. 

CHAPTER XXXII 

Mill and By-products. — Sources ; Wheat by-products ; Wheat 
bran ; Wheat shorts ; Wheat germ ; Wheat screenings ; Linseed 
meal ; Cottonseed cake and meal ; Oat feed ; Gluten meal ; Malt 
sprouts ; Miscellaneous by-products ; Inspection of feeding stuffs ; 
Problems and experiments. Pages 291-298. 

CHAPTER XXXIII 

Roots, Tubers, and Fruits. — General composition ; Potatoes ; Car- 
rots ; Parsnips ; Mangel wurzels ; Apples ; Oranges ; Lemons ; 
Strawberries ; Grapes ; Olives ; Dried fruits ; Miscellaneous fruits ; 
Food value. Pages 299-303. 

CHAPTER XXXIV 

Fermentation. — Insoluble ferments ; Soluble ferments or en- 
zymes ; Aerobic and anaerobic ferments ; Conditions necessary for 
fermentation ; Soil ferments ; Ferments in seeds ; Ferments in bread- 
making ; Ferment action and food digestion ; Ferments and food 
preservation; Ferments in butter- and cheese-making; Disease- 
producing organisms; Beneficial organisms; Experiments. Pages 
304-310. 

CHAPTER XXXV 

Chemistry of Digestion and Nutrition. — Digestion, a biochemical 
process ; Digestion experiments ; Caloric value of foods ; Available 



CONTENTS XV11 

energy of foods ; Net energy of foods ; Digestion of proteids ; Di- 
gestion of the carbohydrates ; Digestion of fats ; Oxygen necessary 
for digestion ; Factors influencing digestion ; Mechanical condi- 
tion ; Combination of foods ; Amount of food consumed ; Palata- 
bility; Individuality; Miscellaneous factors influencing digesti- 
bility ; Application of digestion coefficients ; Digestible nutrients 
of foods; Problems. Pages 311-327. 

CHAPTER XXXVI 

Rational Feeding of Animals. — Balanced rations ; A maintenance 
ration ; Standard rations ; Food requirements of animals ; Food 
supply at different stages of growth ; Food requirements of horses ; 
Selection of food for horses ; Foods required for beef production ; 
Selection of foods for beef production ; Food requirements of dairy 
cows ; Selection of foods for dairy cows ; Food requirements of 
swine ; Food requirements of sheep ; Calculation of balanced 
rations ; Nutritive ratio ; Comparative cost and value ; Caloric 
value of rations ; Sanitary conditions ; Problems. Pages 328-347. 

CHAPTER XXXVII 

Composition of Animal Bodies. — Water and dry matter ; Mineral 
matter ; Fat ; Nitrogenous matter ; Proteids of meat ; Albumin ; 
Myosin ; Syntonin ; Hemoglobin ; Insoluble proteids ; Peptones ; 
Keratin ; Albuminoids ; Gelatin ; Influence of food upon the com- 
position of animal bodies ; Composition of human body. Pages 

348-355- 

CHAPTER XXXVIII 

Rational Feeding of Men. — Similarity of the principles of human 
and animal feeding ; Dietary standards ; Amount of food con- 
sumed per day ; Calculating a balanced ration ; Comparative cost 
and value of foods ; Factors influencing digestibility ; Requisites of 
a ration ; Dietary studies ; Chemical changes in the cooking of 
foods ; Refuse and waste matters ; Loss of nutrients in the prep- 
aration of foods ; Mineral matter in a ration ; Digestibility of 
foods ; Digestibility of animal foods ; Digestibility of vegetable 
foods ; Relation of food to health ; Tables of composition of human 
foods. Pages 356-380. 



XVI CONTENTS 



CHAPTER XXX 



Maize (Indian Corn). — Structure of the kernel; Composition; 
Proteids ; Nitrogenous and non-nitrogenous corn ; Varieties ; 
Moisture content of corn ; Corn products ; Corn as a food ; Experi- 
ments. Pages 273-278. 

CHAPTER XXXI 

Oats, Barley, Rye, Buckwheat, Rice, and Miscellaneous Seeds. — 

Structure of the oat kernel ; Composition of oats ; Oats as human 
and animal foods ; Barley ; Rye ; Rice ; Buckwheat ; Millet seed ; 
Peas and beans; Grading of grains; Experiments. Pages 279-290. 

CHAPTER XXXII 

Mill and By-products. — Sources ; Wheat by-products ; Wheat 
bran ; Wheat shorts ; Wheat germ ; Wheat screenings ; Linseed 
meal ; Cottonseed cake and meal ; Oat feed ; Gluten meal ; Malt 
sprouts ; Miscellaneous by-products ; Inspection of feeding stuffs ; 
Problems and experiments. Pages 291-298. 

CHAPTER XXXIII 

Roots, Tubers, and Fruits. — General composition ; Potatoes ; Car- 
rots ; Parsnips ; Mangel wurzels ; Apples ; Oranges ; Lemons ; 
Strawberries ; Grapes ; Olives ; Dried fruits ; Miscellaneous fruits ; 
Food value. Pages 299-303. 

CHAPTER XXXIV 

Fermentation. — Insoluble ferments ; Soluble ferments or en- 
zymes ; Aerobic and anaerobic ferments ; Conditions necessary for 
fermentation ; Soil ferments ; Ferments in seeds ; Ferments in bread- 
making ; Ferment action and food digestion ; Ferments and food 
preservation ; Ferments in butter- and cheese-making ; Disease- 
producing organisms; Beneficial organisms; Experiments. Pages 
304-310. 

CHAPTER XXXV 

Chemistry of Digestion and Nutrition. — Digestion, a biochemical 
process ; Digestion experiments ; Caloric value of foods ; Available 



CONTENTS XV11 

energy of foods ; Net energy of foods ; Digestion of proteids ; Di- 
gestion of the carbohydrates ; Digestion of fats ; Oxygen necessary 
for digestion ; Factors influencing digestion ; Mechanical condi- 
tion ; Combination of foods ; Amount of food consumed ; Palata- 
bility; Individuality; Miscellaneous factors influencing digesti- 
bility ; Application of digestion coefficients ; Digestible nutrients 
of foods ; Problems. Pages 311-327. 

CHAPTER XXXVI 

Rational Feeding of Animals. — Balanced rations ; A maintenance 
ration ; Standard rations ; Food requirements of animals ; Food 
supply at different stages of growth ; Food requirements of horses ; 
Selection of food for horses ; Foods required for beef production ; 
Selection of foods for beef production ; Food requirements of dairy 
cows ; Selection of foods for dairy cows ; Food requirements of 
swine ; Food requirements of sheep ; Calculation of balanced 
rations ; Nutritive ratio ; Comparative cost and value ; Caloric 
value of rations; Sanitary conditions; Problems. Pages 328-347. 

CHAPTER XXXVII 

Composition of Animal Bodies. — Water and dry matter ; Mineral 
matter ; Fat ; Nitrogenous matter ; Proteids of meat ; Albumin ; 
Myosin ; Syntonin ; Hemoglobin ; Insoluble proteids ; Peptones ; 
Keratin ; Albuminoids ; Gelatin ; Influence of food upon the com- 
position of animal bodies ; Composition of human body. Pages 

348-355- 

CHAPTER XXXVIII 

Rational Feeding of Men. — Similarity of the principles of human 
and animal feeding ; Dietary standards ; Amount of food con- 
sumed per day ; Calculating a balanced ration ; Comparative cost 
and value of foods ; Factors influencing digestibility ; Requisites of 
a ration ; Dietary studies ; Chemical changes in the cooking of 
foods ; Refuse and waste matters ; Loss of nutrients in the prep- 
aration of foods ; Mineral matter in a ration ; Digestibility of 
foods ; Digestibility of animal foods ; Digestibility of vegetable 
foods ; Relation of food to health ; Tables of composition of human 
foods. Pages 356-380. 



INTRODUCTION 

Plant life and animal life are dependent upon the changes 
which are continually taking place in nature. The laws 
of nature, as far as they are known, are set forth in 
the various sciences, among which chemistry occupies 
a prominent place. In everyday life affairs, chemistry 
takes an important part because it is the science which 
treats of the composition and uses of substances found 
in nature. Plant and animal foods which are essential 
for life are simply mechanical mixtures of various forms 
of matter which are constantly undergoing changes and 
exemplifying the laws of chemistry. In agriculture, 
chemistry takes an important part, the term Agricultural 
Chemistry being applied to that branch of the science 
which concerns itself with the practical application of the 
laws of chemistry to the science of agriculture. 

In the cultivation of the soil, production of crops, feed- 
ing of animals, manufacture of farm products, prepara- 
tion and use of human foods, and in all life processes, 
numerous chemical changes take place, and it is in part 
the province of chemistry to investigate these changes so 
as to assist nature in rendering the plant food of the soil 
more available, and to produce crops of the highest nu- 
tritive value, as well as to indicate ways in which the 
best possible use can be made of farm products in the 
feeding of animals and men. Before these subjects can 

xix 



XX INTRODUCTION 

be considered in an intelligent way, a fundamental knowl- 
edge must be obtained of some of the basic principles and 
laws of chemistry, since they are as essential to future 
work along special lines as is a good foundation to a 
building, or a scaffold during its construction. In the 
household, arts, industries, and professions, constant use 
is made of products formed from the soil, air, and water. 
In order to understand more perfectly the nature of the 
substances dealt with so as to make the most intelligent 
use of them, it is necessary to have a practical knowledge 
of some of the laws of chemistry and of the properties of 
the elements and the compounds which enter into the 
composition of plant and animal bodies. 

To the student who begins the study of chemistry, it 
is imperative that the first part of the subject should be 
thoroughly mastered. Chemistry is different in its nature 
from many subjects. It cannot be studied in discon- 
nected parts, but must be undertaken systematically. It 
cannot be absorbed by listening to lectures, but must be 
studied. If the first part of the work is neglected, failure 
is almost inevitable. If particular attention is given to 
the elements and their combinations, to the composition 
of matter, to laboratory manipulations, and to the classi- 
fication of the elements, and if the experiments are per- 
formed regularly, the student experiences a keen enjoy- 
ment in the subject, the work ceases to be drudgery and 
becomes a pleasure. 

Should it be desired to begin the laboratory practice 
with the classroom study, Sections 15 to 21 of Chapter 2 
may be deferred or studied with Chapters 4, 5, and 6. 

The student should make an effort to learn how to 
study ; the memorizing of chemical formulas and equa- 
tions is not studying chemistry; he should master the 



INTRODUCTION XXI 

principles governing the combination of elements and 
then the memorizing of chemical formulas becomes un- 
necessary. In the preparation of the lessons, there are a 
number of reference books which should be consulted 
occasionally. For example, if difficulty is experienced 
with the subject of valence and radicals, the interesting 
chapter upon these topics in Ellen H. Richards' " Chemis- 
try of Cooking and Cleaning " should be read. Remsen's 
" Chemistry," Hart's " Chemistry for Beginners," Storer 
and Lindsay's " Elementary Manual of Chemistry," as 
well as many others, will be found valuable. In study- 
ing the parts relating to foods, crops, and animal feeding, 
Henry's " Feeds and Feeding," Jordan's " Feeding of 
Farm Animals," Armsby's " The Principles of Animal 
Nutrition," Johnson's " How Crops Grow," and " How 
Crops Feed," and the bulletins of the U. S. Department 
of Agriculture and of the several stations should be avail- 
able. The student should early acquire the habit of con- 
sulting other works, as frequently a topic is presented 
more clearly in one work than in another. 

He who studies chemistry from the professional point 
of view, as medical chemistry, pharmaceutical chemistry, 
or agricultural chemistry, should remember that because 
of the limited time for the subject in professional schools, 
he is receiving at the best only a very abridged course in 
the science. Hence the necessity of supplementing it by 
collateral reading and study ; otherwise he comes in 
contact with but one phase of the subject, and while he 
receives a technical education, he may obtain only a limited 
and narrow view of the science of chemistry. 

In the study of the " Chemistry of Plant and Animal 
Life," it is the aim to bring the student into close contact 
with nature. This is one of the requisites for perfect agri- 



XX11 INTRODUCTION 

culture. Although not all of the laws relating to the chem- 
istry of plant and animal life have been discovered, many 
of those relating to soils and foods, particularly human 
foods, are known and can be applied, to everyday life 
affairs. 



PART I 



CHAPTER I 
Composition of Matter 

i. Physical and Chemical Changes. — All substances 
in nature are subject to change in form and composition. 
At a low temperature water is converted into ice, and by 
the application of heat, into steam. The three forms 
which water assumes, solid, liquid, and vapor, are merely 
the different conditions in which it is capable of exist- 
ing. When water is changed to steam or ice, noth- 
ing is added to or taken from the particles of water, 
simply a change of form or a physical change takes place. 
When, however, an electric current is passed through 
water, the water is decomposed and two gases are pro- 
duced. When such a change occurs the water par- 
ticles are subjected to a change in composition called a 
chemical change. 

Limestone may be pulverized until it is as fine as wheat 
flour, and when examined with a microscope, each frag- 
ment is in all respects like the original piece, except in 
size. The crushing has resulted merely in dividing the 
limestone into a large number of particles. If, however, 
a piece of limestone is burned in a lime kiln, the product 
is entirely different in its properties from the original 
lime rock. When water is added to burned lime, the lime 
slakes, heat is generated, and steam is given off, while, 
when water is added to lime rock, no appreciable change 
takes place. 

Changes which affect the form but not the composition 

3 



4 AGRICULTURAL CHEMISTRY 

of matter are known as physical changes. The produc- 
tion of steam from water, the freezing of water, the pul- 
verizing of limestone, and similar changes which do 
not affect the composition of the material are physical 
changes. When milk sours, fruits decay, or wood is 
burned, a different kind of change takes place. The 
smallest particles of which the material is composed 
undergo change in composition. The products formed 
are entirely different in character from the original sub- 
stances. Such changes affect the identity or individuality 
of a material, and are chemical changes. 

2. Physics is the science which concerns itself with the 
changes which matter undergoes when the ultimate par- 
ticles of a material retain their identity or individuality. 

Animal and plant life are to a great extent dependent 
upon the physical changes which take place in the soil. 
Rain is the result of the action of physical agencies, as is 
also the pulverization of rocks and soils. In all manu- 
facturing operations, and as the result of all kinds of 
manual labor, particularly upon the farm and in the 
workshop, physical changes are continually taking place. 

3. Chemistry is the science which deals with the 
changes which matter undergoes when the ultimate par- 
ticles lose their identity or individuality, and the prod- 
ucts formed are entirely different from the original mate- 
rial. 

Chemical changes are continually taking place, and plant 
growth and animal life are dependent largely upon the 
chemical changes as well as upon the physical changes which 
occur in the soil and in the air. Life processes are inti- 
mately associated with chemical changes. Chemical and 
physical changes are closely related ; a chemical change 
is often dependent upon a physical change, and a physi- 



COMPOSITION OF MATTER 5 

cal change is, in turn, often dependent upon a chemical 
change. A chemical change necessarily brings about a 
physical change. While the sciences of chemistry and 
physics are, to a certain extent, closely related, each 
nevertheless deals with a different phase of change which 
matter undergoes. 

4. Indestructibility of Matter. — When either a chem- 
cal or a physical change takes place, no matter is destroyed 
or produced. It is not possible either to create or destroy 
matter. This is known as the law of indestructibility of 
matter. 

Whenever a chemical change takes place, the parts 
which make up the substance are rearranged in a new and 
different way, or they are combined with other materials. 
When wood is burned, it is changed into gaseous prod- 
ucts and ashes ; the materials which composed the wood 
are not lost to nature, they simply assume a different 
form. The law of indestructibility of matter is one of the 
foundation principles of chemistry. It was believed, 
at one time, that metals, as copper, could be changed to 
gold, and other substances to different forms of matter. 
After many centuries of experimenting, it was found 
that this could not be done, and as the result, the law of 
indestructibility of matter was established. 

5. Molecules. — It is possible, by mechanical means, as 
pulverizing, to reduce substances to a very fine state of 
division, and it is believed that if this division could be 
carried on by more refined methods, particles of mat- 
ter could finally be obtained that would not be suscepti- 
ble to further division by purely physical methods. The 
smallest particle of a material that can exist and have all 
of the properties of the original material is called a mole- 
cule. Molecules, however, have never been separated as 



6 AGRICULTURAL CHEMISTRY 

individuals. All forms of matter are composed of mole- 
cules. The proof that matter is composed of molecules 
is founded upon the laws of physics. The reasons for 
the acceptance of the molecular structure of matter can- 
not profitably be studied by the student of elemen- 
tary chemistry, but properly form a very important part 
of advanced chemistry. The molecular structure of 
matter has been sufficiently well established to warrant 
the use of the term molecule by the student of elemen- 
tary chemistry. 

6. Atoms. — Whenever a chemical change takes place, 
the molecule is changed in composition. When an elec- 
tric current is passed through water, the molecules of 
water are split up into simpler forms of matter. It is 
evident that the molecule is not the simplest form of mat- 
ter, and that while the molecule is the smallest part of a 
substance, it is, in fact, made up of still smaller parts. 
These parts of matter which form a molecule are called 
atoms. An atom is the smallest part of an elementary 
substance that can enter into combination to form a 
molecule. Atoms never exist in nature in a free or un- 
combined state, but unite to form molecules, and mole- 
cules unite to form masses. 

7. Elements. — The simplest forms of matter, as iron, 
copper, and sulfur, from which it is impossible to extract 
or obtain simpler bodies, are called elements. The ele- 
ment is the simplest form in which matter can exist. 
All substances found in nature, as plant and animal bod- 
ies, rocks and soils, are composed of compounds which, 
in turn, are composed of elements. There are about 74 
of these elementary forms of matter, although only about 
18 take any important part directly or indirectly, as far 
as is known, in either plant or animal life processes. 



COMPOSITION OF MATTER 7 

There are a few substances found in nature in elementary 
form, as iron, copper, gold, and sulfur, but most of the 
elements are in combination with others, forming com- 
pounds. 

8. Compounds. — The substances found most abun- 
dantly in nature are compounds. A compound is formed 
by the chemical union of two or more elements. All 
compounds are made up of a definite amount, by weight, 
of separate elements which unite according to the laws of 
chemical combination. Water, for example, is a com- 
pound formed by the union of two elements, hydrogen 
and oxygen. Sugar is a compound of three elements, 
hydrogen, carbon, and oxygen. When elements unite to 
form a compound, the elements lose their identity and 
the compound that is produced has entirely different and 
distinct chemical and physical properties from those of 
the elements of which it is composed. 

9. Chemical Affinity. — The force or power which 
causes elements to combine to form compounds is called 
chemical affinity, and about this comparatively little is 
known. Whenever a compound is separated into its ele- 
ments, chemical affinity or the force which holds the 
elements together is overcome. When elements com- 
bine to form compounds, it is because of the chemical 
affinity which the elements have for one another. Some 
elements have a stronger affinity for certain elements than 
for others. 

10. Mechanical Mixtures. — When two or more sub- 
stances mix, but fail to unite chemically, a mechanical 
mixture is obtained. When iron and sulfur are mixed, 
a mechanical mixture is the result, and the iron and the 
sulfur can, by purely physical methods, be separated. 
If, however, a mixture of iron and sulfur is heated, a 



8 AGRICULTURAL CHEMISTRY 

chemical change takes place and it is impossible by physi- 
cal methods, as by the use of a magnet or by solvents, to 
separate the iron from the sulfur. Compounds as well 
as elements may form mechanical mixtures. 

ii. Chemical Analysis and Synthesis. — Whenever a 
substance or a compound is separated into simpler com- 
pounds or elements, the process is called chemical analy- 
sis. When only the kinds of elements or simpler com- 
pounds are determined, the process is called qualitative 
analysis. If the percentage amounts are determined, it 
is called quantitative analysis. When elements or simpler 
compounds are united, the process is called synthesis. 
Synthesis and analysis are directly opposite processes. 
When substances are produced in the laboratory from 
simpler elements or compounds, it is called a synthetical 
process. Many useful compounds are produced syntheti- 
cally. 

12. Summary. — Substances may undergo either phys- 
ical or chemical changes. A physical change does not 
destroy the identity or change the composition of the 
molecule. When a chemical change occurs, the atoms 
are combined in a different way and a new molecule is 
produced. The molecule is the smallest particle of mat- 
ter that can exist and retain its identity or individuality. 
Compounds are composed of molecules, and molecules are 
composed of atoms. Atoms never exist free, but unite 
to form molecules. If a substance contains in its mole- 
cule atoms of only one kind, it is an element. If there 
are present atoms of more than one kind, it is a com- 
pound. Physics and chemistry are closely related sciences, 
but each deals with a different kind of change. Life 
processes are dependent largely upon the physical and 
chemical changes continually taking place in nature. 



CHAPTER II 

Properties of Elements and Compounds 

13. Physical Properties. — In order to determine the 
value of any element or compound, a knowledge of its 
chemical and physical properties is necessary, and it is 
important that a clear idea be obtained as to what is 
meant by the terms chemical and physical properties of 
elements and compounds. Each element and compound 
has its own characteristic properties, which are different 
in a number of ways from those of other elements and 
compounds. The physical properties of a substance in- 
clude : 

1. Form or state of the material, as solid, liquid, or 
gas, which depends upon the temperature to which the 
substance is subjected. Many substances which are solid 
under ordinary conditions are, at higher temperatures, 
converted into liquids or vapors ; and substances which 
are gases are in turn converted into liquids and solids at 
low temperature and under high pressure. 

2. Weight or specific gravity. The weight or specific 
gravity of a material depends upon its molecular struc- 
ture and upon the character of its individual molecules. 
Some of the elements and compounds have molecules of 
greater weight than have others. Liquids and gases are 
characterized as light or heavy according to their weight, 
compared with some material taken as the standard. 

3. Color. The color of a compound is a physical prop- 
erty which is due to its chemical composition. Many of 

9 



10 AGRICULTURAL CHEMISTRY 

the elements, as copper, silver, and gold, have character- 
istic colors. Some compounds owe their value entirely to 
their color, and are used for paints and dyes. 

4. Odor and taste. Odor and taste of an element or 
a compound are physical properties which are character- 
istic of the element or compound. 

5. Electrical characteristics. Elements and compounds 
have definite electrical properties. They are either good or 
poor conductors of electricity, and offer a large or a small 
amount of resistance to the passing of an electric current. 

The way in which a substance responds to pressure, 
water, heat, and cold depends upon its physical proper- 
ties, and the physical properties in turn are modified by 
these agencies. 

In a study of the elements and their compounds, the 
physical properties are also included because our knowl- 
edge of chemistry would be incomplete without consider- 
ing the physical as well as the chemical properties of 
substances. 

14. Chemical Properties. — In addition to the physical 
properties, each element and compound has definite chem- 
ical properties. This is because the molecules of the 
different elements are unlike in character, and some of the 
elements and compounds are more readily affected by 
chemical agencies than are others. The molecules of 
compounds are made up of atoms of different kinds which 
impart different properties to the molecule. Copper, for 
example, has different chemical properties from gold. It 
will dissolve more readily in acids, tarnish in the air, and 
be acted upon more rapidly by other bodies than will 
gold. When iron is exposed to moisture and air it rusts, 
while aluminum is not readily affected by these agents. 
This is because iron and aluminum have different chem- 



ELEMENTS AND COMPOUNDS II 

ical properties. The chemical properties of a substance 
include the way in which it combines or produces chem- 
ical change when brought into contact with other ele- 
ments or compounds. Some elements are characterized 
as chemically active or inactive. An active element is 
one that readily unites or combines with other elements, 
while an inactive or passive element is one that does not 
readily unite or combine. Some elements are active 
under certain conditions and with some of the elements, 
and inactive under other conditions and with other ele- 
ments. The various elements require different conditions 
for producing chemical changes. In studying an element, 
the way in which it deports itself in producing chemical 
changes, the ability with which it combines with other 
elements, and the products which are formed as the re- 
sult of the chemical changes are some of the important 
chemical properties considered. 

A study of the chemical and the physical properties of 
elements and their compounds is important in many ways, 
as the value of a substance depends entirely upon its 
properties. In the growing and cultivation of crops, the 
production, preparation, and the economic use of foods, 
the treatment of diseases, and ;n all manufacturing opera- 
tions, as the smelting and refining of metals, the chemical 
and physical properties of the elements and their com- 
pounds are constantly made use of. 

15. Symbols of the Elements. — In the study of chem- 
istry, a characteristic system of notation is used. The 
name of an element, as oxygen, is not written in full, but 
a symbol or sign, denoting the element, is employed. In 
the case of oxygen, the symbol is 0. The symbol of an 
element is either the first letter of the name of the ele- 
ment, or the first with some characteristic letter, as CI 



12 



AGRICULTURAL CHEMISTRY 



for chlorin. In some cases, the symbols are derived from 
the Latin names of the elements, as Fe (Ferrum) for iron. 
By use, the student soon becomes familiar with the sym- 
bols most commonly used. 

Name Symbol 

Aluminum Al 

Antimony Sb 

Arsenic As 

Barium Ba 

Bismuth Bi 

Boron B 

Bromin Br 

Calcium Ca 

Carbon C 

Chlorin CI 

Chromium Cr 

Cobalt Co 

Copper Cu 

Fluorin F 

Gold Au 

Hydrogen H 

Iodin I 

Iron Fe 

Lead Pb 

Lithium Li 

Magnesium Mg 

Manganese Mn 

Mercury Hg 

Nickel Ni 

Nitrogen : N 

Oxygen O 

Phosphorus P 

Platinum Pt 

Potassium K 

Silicon Si 

Silver Ag 

Sodium Na 

Sulfur S 

Tin Sn 

Zinc Zn 



Approximate 


Va- 


Kind of 


atomic weight 


lence 


element 


27 


3 


Base-forming 


I20.5 


3, 5 




75 


3, 5 




137-5 


2 


Base-forming 


208 


3, 5 




11 


3 


Acid-forming 


80 


1 


Acid-forming 


40 


2 


Base-forming 


12 


2, 4 


Acid-forming 


35-5 


1 


Acid-forming 


52 


4, 6 




59 


2, 4 


Base-forming 


64 


i, 2 


Base-forming 


19 


1 


Acid-forming 


197 


3 


Base-forming 


127 


1 


Acid-forming 


56 


2, 3i 4 


Base-forming 


207 


2, 4 


Base-forming 


7 


1 


Base-forming 


24 


2 


Base-forming 


55 


2, 4, 6 




200 


1, 2 


Base-forming 


59 


2, 4 


Base-forming 


14 


3. 5 


Acid-forming 


16 


2 


Acid-forming 


3i 


3. 5 


Acid-forming 


195 


4 


Base-forming 


39 


1 


Base-forming 


28 


4 


Acid-forming 


108 


1 


Base-forming 


23 


1 


Base-forming 


32 


2, 4 


Acid-forming 


119 


2, 4 


Base-forming 


65.5 


2 


Base-forming 



ELEMENTS AND COMPOUNDS 13 

16. Formulas of Compounds. — Since compounds are 
composed of elements, it is possible, by means of combi- 
nation of symbols, to express the formula of a compound. 
The formula of a compound denotes the number and 
kinds of elements contained ; as, for water, the formula 
H 2 designates that the compound is composed of the 
two elements hydrogen and oxygen ; and for sugar, the 
formula C12H22O11 denotes that the compound is made up 
of three elements, carbon, hydrogen, and oxygen. The 
formula always expresses the composition. In the for- 
mulas of compounds, figures are made use of, as 2 in H 2 0, 
at the right of the H and partially below the line. In 
this formula, the 2 indicates that there are two atoms of 
H in the molecule. In the case of sugar, the figures used 
mean that in one molecule of sugar there are 12 atoms of 
C, 22 atoms of H, and n of O. The formula of a com- 
pound always represents one molecule of the compound 
unless some figure is placed to the left of the formula, as 
2 H 2 0. When placed in this position, the 2 shows that 
there are two molecules of water. Figures placed at 
the left of a formula and on the same line indicate the 
number of molecules, while figures at the right of the in- 
dividual element represent the number of atoms of ele- 
ments in each molecule. Hence the formula of a com- 
pound always designates the composition of the molecule, 
and the number and kind of atoms contained. Further 
study of the formulas of compounds will show that addi- 
tional facts, as composition by weight and volume, are 
also represented. 

Exercise. — Name the elements, the number of molecules, 
and the number of atoms in each molecule in the following 
formulas : NaCl, CaCl 2 , 2 KC1, 2 K 2 S0 4 , A1 2 3 , 5 N 2 5 , H 2 S0 4 , 
NaOH, HPO3. 



14 AGRICULTURAL CHEMISTRY 

17. Atomic Weights. — An atom is the smallest part of 
an element present in a molecule. Atoms have definite 
properties, as weight. Hydrogen is the lightest material 
known. An atom of hydrogen, or the smallest part of 
hydrogen which can enter into chemical combination, is 
considered as having a weight of 1. The weight of the 
atom of any element is the number of times heavier that 
atom is than hydrogen, which is the standard. Oxygen, 
for example, has an atomic weight of 16 ; that is, an atom 
of oxygen weighs 16 times as much as an atom of hydro- 
gen. Carbon has an atomic weight of 12; that is, an 
atom of carbon is 1 2 times as heavy as an atom of hydro- 
gen. The way in which the atomic weights are obtained 
cannot, at this stage of the work, be profitably considered. 
Atomic weights are, however, obtained with a high de- 
gree of accuracy, and while the individual atoms and 
molecules are not susceptible, at the present time, to sep- 
aration and weighing, the comparative weight, or the 
number of times heavier or lighter a definite number of 
molecules is than a similar number of molecules, in other 
forms of matter, can be accurately determined. While 
the absolute weight of a molecule or atom cannot be 
determined, its comparative weight can be. When chlo- 
rin, for example, combines with hydrogen, it is known 
that 35.45 times as much, by weight, of chlorin as of 
hydrogen has entered into combination. Hence the 
smallest part by weight of chlorin which can combine 
must weigh at least 35.45 times as much as the weight of 
the smallest particle of hydrogen which enters into com- 
bination. The atomic weights of the more common ele- 
ments are given in the table on page 12. 

18. Molecular Weights. — Since the molecules of com- 
pounds are composed of a definite number of atoms of 



ELEMENTS AND COMPOUNDS I 5 

elements, and each atom has a definite weight, it neces- 
sarily follows that a molecule has a definite weight. In 
the case of water, the formula H 2 represents one mole- 
cule of water, composed of two atoms of hydrogen and 
one of oxygen. As the atoms have definite weights, the 
weight of the molecule H 2 is the sum of the weights of 
the atoms in the molecule. Since hydrogen is taken as 
the standard and weighs i, and there are two atoms of 
hydrogen, and one atom of oxygen weighing 16, the 
weight of the molecule will be 2 + 16 or 18 ; that is, the 
molecule of water, H 2 0, is 18 times heavier than one 
atom of hydrogen. 

Exercise. — Compute the molecular weights of the compounds 
given in the exercise following the formulas of the compounds, Sec- 
tion 16. 

19. Law of Definite Proportion. — A study of the com- 
bination of elements shows that when elements unite 
to form compounds, a definite weight of each element 
enters into the composition. This is known as the law 
of definite proportion. Chemical combination always 
takes place between definite weights of the elements, and 
a chemical compound always contains the same elements 
in exactly the same proportion by weight. The law of 
definite proportion is one of the fundamental principles of 
modern chemistry, and has enabled the chemist to deter- 
mine the composition of bodies. This law is founded 
upon fact independent of any hypothesis, and the accu- 
racy of the law has been demonstrated by many investi- 
gators. 

The theories relating to the composition of matter, par- 
ticularly to atoms and molecules, are in harmony with 
this law of definite proportion. It is believed, since 
chemical combination occurs between definite masses 



1 6 AGRICULTURAL CHEMISTRY 

of elements, it must also occur between the smallest 
particles of the substances. Since the smallest particles 
which enter into chemical composition are the atoms, 
then chemical combination must take place between the 
atoms. The atoms all possess definite weights. Hence 
it can readily be understood why chemical combination 
takes place between definite weights of the elements. The 
next step in the study of the composition of matter is the 
way in which the elements combine, or the power of com- 
bination ; this is known as valence. 

20. Valence. — The valence of elements is the power 
which an atom of one element has of holding in chem- 
ical combination a definite number of atoms of other ele- 
ments. Carbon, for example, has the power of uniting 
with or holding in chemical combination four hydrogen 
atoms ; carbon is said, therefore, to have a valence of 4. 
Elements which have power to hold only one atom of 
hydrogen in combination are called monovalent. Hydro- 
gen is a monovalent element. Bivalent, trivalent, tetra- 
valent, and pentavalent elements are those whose atoms 
have the power of uniting with 2, 3, 4, and 5 atoms of 
hydrogen or other monovalent elements. The valence 
of an element is spoken of as its combining power. Some 
of the elements have more than one valence. The va- 
lences of some of the elements are given on page 12. 

21. Combination of Elements. — The combination of 
two elements to form compounds is always governed by 
the valence of the elements. When calcium and chlorin 
combine, the combination takes place in a definite way ; 
calcium has a valence of 2 ; chlorin has a valence of 1 ; 
hence, in order to make a chemical combination, it will 
take one atom of Ca, having a valence of 2, to combine 
with two atoms of CI, each CI atom having a valence 



ELEMENTS AND COMPOUNDS 1 7 

of i. CaCl 2 is the formula. Calcium could not combine 
with three atoms of chlorin, because compounds com- 
posed of two elements are always formed according to the 
valence of the elements. The valence of calcium, 2, lim- 
its the number of atoms of chlorin with which it can com- 
bine. If one of the elements, as oxygen, has a valence 
of 2, and the other element, as carbon, has a valence of 
4, 2 atoms of oxygen, each atom having a valence of 2, 
will be required to combine with 1 atom of carbon, hav- 
ing a valence of 4. The formula is CO2. In the for- 
mulas of compounds, the valences of the atom's uniting 
are always balanced or satisfied. 

When two elements combine, and one of them has an 
odd valence, as phosphorus, which has a valence of 3, 
two atoms of the element with the odd valence are always 
required for combination. For example, two phosphorus 
atoms, each having a valence of 3, making a total valence 
of 6, require, in order to combine with 0, whose valence 
is 2, three atoms of 0, which make the valence of 6. The 
two atoms of phosphorus combine with the three atoms 
of oxygen, making a balanced compound, and the va- 
lences of the phosphorus and oxygen are satisfied. The 
compound is P2O3. 

Combine according to the lowest valence the following 
elements, and give the formulas of the compounds pro- 
duced : 

Zinc and oxygen Sulfur and oxygen 

Calcium and oxygen Sodium and chlorin 

Tin and oxygen • Potassium and chlorin 

Iron and oxygen Carbon and oxygen 

Potassium and oxygen Phosphorus and oxygen 

Silicon and oxygen Iron and sulfur 

Potassium and sulfur 

Manganese and sulfur 



1 8 AGRICULTURAL CHEMISTRY 

Phosphorus and hydrogen 
Calcium and chlorin 
Aluminum and oxygen 
Phosphorus and oxygen 

Problem i. — How much hydrogen is required to combine with 
20 grams of to form H 2 ? When hydrogen and oxygen unite to 
form water, the combination takes place according to valence, as 
follows : 2 atoms of H + 1 atom of equal 1 molecule of water, 
or 2H + O = H 2 0. An atom of weighs 16 times as much as 
an atom of H. Two atoms of H and 1 atom of O weigh 18 times as 
much as an atom of H. The molecular weight of water is 18. Six- 
teen of these 18 parts, by weight, are 0, or jf are oxygen, which 
is 88.88 per cent; T 2 g, or 11.12 per cent, being H. In the pro- 
duction of water, H and O always unite in this proportion. If, 
for example, 20 grams of and 2 grams of H were brought together, 
only 16 grams of would enter into chemical combination with the 
2 grams of H, and 4 grams of would be left uncombined. The 
amount of H required to combine with 20 grams of would be 
obtained from the following proportion, — 2 : 16 : : x : 20, or x = 2.5 
grams of H. 

Problem 2. — (1) Calculate the per cent by weight of C and O in 
C0 2 . (2) Calculate the per cent of Fe and in Fe 2 3 . (3) Cal- 
culate the per cent of in KCIO3. 



CHAPTER III 
Laboratory Manipulation 

22. Importance of Laboratory Practice. — Laboratory 
practice is an essential part of the study of chemistry. 
It assists in developing more perfect ideas in regard to 
the composition of substances, and many of the important 
facts and laws of chemistry may be demonstrated by the 
student. The hand, the eye, the nose, and, to a less 
extent, the ear are all called into use in the laboratory, 
and this results in a balanced education of the senses. 
Neatness is absolutely necessary for success in laboratory 
work. An experiment performed in a slovenly way, 
with dirty and poorly connected apparatus, and poor 
mechanical manipulation, fails to give the right impres- 
sion or result. 

When laboratory work is in progress it should receive 
the student's entire attention. The directions for the 
experiments should be carefully followed. The appara- 
tus should always be put together as directed, and be- 
cause of the danger of accident, the student should never 
take the risk of connecting apparatus in an original way, 
or of using for the experiment materials other than those 
directed. The student should never attempt to experi- 
ment for himself in combining chemicals. 

23. Names and Uses of Apparatus. — The various 
pieces of apparatus used in the experiments are shown in 
Plates I and II. Number 21 shows the common Bunsen 
burner, and, at the right, the wing-top attachment, used 

19 



20 AGRICULTURAL CHEMISTRY 

in bending glass tubes. Number 24, Plate II, is an iron 
ring stand with three rings, and No. 25 is a single clamp. 
The iron stand with rings is used for supporting appara- 
tus, particularly the sand bath (19) in which there is a 
thin layer of sand. Evaporating dish (5), beaker (12), 
and flask (26) are all supported in the various experi- 
ments upon the sand bath and iron ring stand. In cutting 
glass tubes and perforating corks, the two files (1 and 2) 
are employed. Test tube (13) is used extensively in the 
laboratory, and when heated, is supported with the test- 
tube clamp (18). This test-tube clamp is held in the 
hand. The test tube is cleaned with the test-tube brush 
(17), and when not in use is placed in the test-tube rack 
(14). When solutions are filtered, the funnel (15) is 
used, and is supported in the wooden stand (21). Sub- 
stances are pulverized or mixed in the mortar (16), which 
is supplied with a pestle. The various gases, as oxygen, 
hydrogen, and nitrogen, are collected in the small cylinder 
(10), and in some of the experiments the large cylinder 
(11) is used. The iron spoon (8) is used for ignition of 
substances. Crucible tongs (3) are for handling pieces 
of apparatus when hot. Other pieces of apparatus, 
Woulff bottle (7), water bath (4), tripod (22), Hessian 
crucible (20), wide-mouthed bottle (9), and ground glass 
plate with hole, are used in various ways in the different 
experiments. Glass rods, thistle tube, pneumatic trough 
(27), of galvanized iron with pocket to receive excess 
of water when cylinders are filled with gas, and small 
squares of plain glass complete the set of apparatus. A 
few pieces, used only occasionally, are obtained from the 
instructor or supply clerk at the time the experiments 
are performed. 

The student should take an inventory of his apparatus 



¥^ ^? 





LABORATORY MANIPULATION 



21 



as soon as assigned a place in the laboratory. In case 
any of the pieces are broken or missing, the attention of 
the instructor should be called to them. Always, at the 
close of each day's work, the apparatus should be 
cleaned, placed in the desk, and the desk locked. The 
apparatus and desk should be kept in a neat and orderly 
condition. Untidiness is a frequent cause of failure in 
laboratory work; neatness and careful attention to 
details are necessary to success. 

24. Cutting Glass Tubing. — Lay the glass tubing on 
the top of the desk or on any other flat surface. Draw 
a sharp three-cornered file across it two or three times, 
always on the same place at which it is to be broken, 
until a scratch is made through the annealed surface of 




Fig 1. — Breaking glass tubing. 

the tubing. Take the tubing in the hands with fingers 
and a thumb on each side of the scratch (see Fig. 1). 
The scratch should be nearly between and on the side 
opposite the thumbs. Pull the hands toward the body 
as if bending the tubing and at the same time press out- 
ward with the thumbs. This causes a square break of the 
tubing. The cut ends of the tubing should then be held in 
the outer portion of a flame until the rough edges are fused. 



22 



AGRICULTURAL CHEMISTRY 



25. Bending Glass Tubing. — Place the wing- top at- 
tachment on the burner. Hold the tubing in the upper 
part of the flame as shown in the illustration (Fig. 2), 





Fig. 3. — Bent tube. 



Fig. 2. — Bending glass tubing. 

and rotate so that all parts are heated alike. When the 
tubing becomes pliable it can be bent in almost any form 
desired, but if overheated it becomes too soft and collapses. 

It is always best to bend with- 
out removing from the flame. 
A little practice with pieces of 
old tubing will soon give the 
necessary experience. Avoid 
twisting or rapid bending of the tube. Make all bends 
on the same plane and aim to make well-rounded joints 
as shown in Fig. 3. 

26. Perforating Corks. — Select a cork of suitable size 
for the test tube or flask used. New corks should always 
be rolled in the cork press. With the small pointed end 
of the round file make a hole through the center of the 
cork, or a little to one side if directed to do so. This 
hole should be perpendicular to the surface of the cork. 
In making a hole, the cork should be held in the left hand, 
and the larger end should be placed against the edge of 




LABORATORY MANIPULATION 27, 

the desk. The file should be held in the right hand, and 

only enough pressure exerted to perforate the cork. The 

opening thus made may be enlarged with the round file 

until the desired size is obtained. The hole should be a 

suggestion smaller than the tube it 

is to receive, which can be inserted 

easily if well annealed and wet. 

When inserting a tube in a cork, never 

push the tube toward the palm of 

the hand, or use too much pressure, 

as severe cuts may be received from 

breaking the glass. Hold the cork in Fig. 4. — inserting glass 

the left hand as shown in Fig. 4, then 

with the right hand carefully insert the tube. Perforated 

rubber stoppers of the requisite size may be used in 

nearly all of the experiments in place of cork stoppers, 

and while the initial cost is more, a saving of time is 

effected. 

27. Weighing. — In this work, the metric system is 
employed, and it is taken for granted that the student is 
familiar with the system ; if he is not, he should review 
the subject as given in any ordinary arithmetic. 

Note. — 1 kilo = 2.2046 lbs. (avoirdupois). 
1 oz. = 28.45 g ms - 
1 lb. = 453-59 gms. 
1 liter = 1.05708 U. S. quarts. 
1 inch = 2.54 centimeters. 
1 meter = 39.3808 inches. 

The small balance used for weighing materials in these 
experiments is shown in Fig. 5. In case 5 grams of a 
material are to be weighed, prepare counterpoised papers, 
about 3 by 4 inches in size ; that is, two pieces of paper 
of exactly the same size to be placed on opposite sides 
of the balance. If they do not weigh alike, remove 



24 



AGRICULTURAL CHEMISTRY 




Fig. 5. — Balance. 



small pieces of the paper from the heavier pan, until the 
needle moves nearly as many divisions on one side of 

the scale as on the other. Then 
place, with the forceps, the 5- 
gram weight on the right-hand 
pan of the balance. Do not 
handle the weights with the 
fingers. By means of the scoop 
or spoon provided for the pur- 
pose, add to the paper in the 
left-hand pan of the balance 
enough of the material that is 
to be weighed to counterpoise 
the 5 -gram weight. If any of 
the substance has been spilled, it should be cleaned up at 
once. The weight should be replaced in the weight box 
and the forceps returned to their proper place. No sub- 
stance except a piece of metal, as copper or lead, should 
ever be placed in direct contact with the balance 
pan. Liquids are never weighed, but always 
measured. Too much care and neatness can- 
not be exercised in weighing. 

28. Measuring Liquids. — For purposes of 
measuring, cylinders or graduates are em- 
ployed (Fig. 6). A large test tube, when 
filled with water, holds from 60 to 65 cc. In 
a measuring cylinder or graduate (Fig. 6), 
measure out 5 cc. of water, and transfer 
to a large test tube. Note the quantity, 
and then pour it out. Now draw water 
directly into the test tube until you have ap- 
proximately the same amount, then measure it. Re- 
peat this operation until you can judge with a fair 



<f^ 



— *> 
I- 'i 

— n 




Fig. 6. — 

Measuring 

cylinder. 



LABORATORY MANIPULATION 



25 



degree of accuracy the part of a test tube filled by 
5 cc. Repeat the operation, using 10, 15, 20, and 25 
cc. portions, until the eye has become reasonably fa- 
miliar with the approximate and relative amounts ; so 
that, if at any time a graduate is not at hand, the 
amounts can be estimated with the eye accurately enough 
for practical purposes. 

29. Obtaining Reagents from Bottles. — Take the 
bottle from the shelf, remove the stopper, holding 
it between the first and 
second fingers of the right 
or left hand (Fig. 7). Hold 
the test tube or vessel that 
is to receive the reagent in 
the other hand. Pour the 
liquid slowly until the de- 
sired amount is obtained. 
Because of danger of con- 
taminating the reagents, it 
is always better to pour the 
liquid slowly and secure the 
right amount at first rather 
than to pour back from the receiving vessel. Replace 
the test tube in the stand or receiver on the desk ; then, 
before inserting the stopper, touch it to the neck of the 
bottle to catch the few drops on the edge, to prevent 
them from dripping down the sides of the bottle, and 
on to the shelf. Be sure to replace the bottle on the 
shelf in its proper place. Much annoyance and delay 
are caused by not returning the bottles to their proper 
places. 

30. Filtering. — Place the funnel on the arm of the 
wooden stand. Fold a filter paper so as to make a semi- 




Fig. 7. — Pouring liquid from bottle. 



26 



AGRICULTURAL CHEMISTRY 



circle (see Figs. 8 and 9). Fold the paper again, forming 
a quadrant (Fig. 10). Then open it as shown in Fig. 





Fig. 8. 



Fig. 9. 
Folding filter paper. 



Fig. id. 



11. Place the filter paper in the funnel, using a little 
water to make it adhere to the sides. Place a beaker or 
cylinder under the funnel so as to 
collect the nitrate, or liquid which 
passes through the filter paper (Fig. 
12). Pour the material to be fil- 
tered into the filter paper in the 
funnel. Do not fill the filter too 
full. An eighth of an inch or so 
should always be left between the 
surface of the liquid and the edge 
of the paper. The stem of the 
funnel should touch the side of the 




Fig. 11. — Folded filter 
paper. 




Fig. 12. — Filtering. 



LABORATORY MANIPULATION 27 

beaker or cylinder so as to avoid spattering. The mate- 
rial left on the filter paper is called the precipitate or 
residue. 

31. Laboratory Notebook. — Each student should 
keep a careful record of his laboratory work. The note- 
book should be complete and should represent the 
student's individual work. With each experiment a 
number of questions are asked, and the record of the ex- 
periment should embody the answers to these questions. 
Do not make short answers, as " yes " and "no," but 
make a complete statement, giving an intelligent answer 
to the question. Do not copy the laboratory directions 
into your notebook, but state briefly and concisely, (i) what 
the experiment is about, (2) the materials used, (3) the 
apparatus employed, (4) what you have observed in mak- 
ing the experiment, (5) the chemical and other changes 
that have taken place, and finally what the experiment 
proves. In writing up the notebook, it is not necessary 
to separate the topics, but all the questions should be 
numbered and answered in the order asked. Write out 
each experiment at the time it is performed, and while 
the work is in progress, watch it and think about it. Do 
not leave or neglect an experiment. When the experi- 
ments are performed as called for from day to day, the 
labor of preparing the daily recitation is considerably 
lessened, and less effort is required to obtain a clear idea 
of the subject. The notebook should be kept in a neat 
and orderly way. Careful attention should be given to 
spelling, English, and punctuation. Always have the 
notebook in condition for examination if the books are 
called for without notice. The instructor will mark all 
errors, and the student should correct them. A note- 
book with errors that have been corrected, representing 



28 AGRICULTURAL CHEMISTRY 

the student's individual work, is much to be preferred to 
a notebook copied from some other student, and having 
but few errors. Each student has an individuality 
which always marks his work, and whenever copying of 
experiments is resorted to, it can be detected by the 
instructor. The student who copies from some one else 
only cheats himself, and usually fails to pass his exam- 
inations. 

32. Breaking of Apparatus. — If due care is taken 
in performing the experiments, there will be but little 
breakage of apparatus. In case an accident occurs, 
clean up the broken pieces at once and place them in the 
waste jar. If a liquid is spilled, wipe it up with a 
sponge, using plenty of water. If a strong acid is spilled, 
a little dilute ammonia should be used in the final 
washing. No combustible materials should be placed 
in the desk, and the student should throw burned 
matches and splinters into the receptacles provided for 
the purpose. 

33. Care of Sinks and Plumbing. — Do not throw waste 
matter of any description, as paper, glass, matches, etc., 
into the sinks. Large waste jars, for such materials, are 
provided under every sink and elsewhere. Everything 
liable to clog the drains must be thrown into these jars. 
Liquids containing acids may be safely thrown into the 
sinks, provided a stream of water is kept running at the 
same time to dilute and wash down the acids. When acids 
are poured into the sinks, care should be taken to prevent 
spattering of the liquid, as severe burns are sometimes 
received when the liquid is not properly poured from the 
vessel. If directions are followed, no accidents can occur. 
Do not fill the sinks too full. The water should never be 
allowed to come to within 2 inches of the top of the 



LABORATORY MANIPULATION 2Q 

sinks. If the sinks overflow, they cause much damage to 
the rooms below. Students who disregard the regula- 
tions in regard to plumbing and the use of sinks will be 
held responsible and must pay for any damage caused by 
carelessness or negligence. 

34. How to Accomplish the Best Results in the Lab- 
oratory. — In order to accomplish the best results, the 
student, while in the laboratory, should endeavor to use 
his time profitably and economically. He should obtain 
a clear idea of what he is to do, and then do it to the best 
of his ability. If the experiment is not a success, repeat 
the work. Never pass over an experiment that offers 
difficulties in performing. Much valuable time can be 
saved by a brief study of the day's work before going 
into the laboratory. While the work is in progress, the 
student should give it undivided attention, and make an 
effort to learn as much as possible from the experiments 
performed. 



CHAPTER IV 

Oxygen 

35. Occurrence. — Oxygen is the most abundant ele- 
ment in nature. About seventy-seven per cent of the 
air, by weight, is free or uncombined oxygen. It enters 
into the composition of water, rocks, and minerals, ana 

plant and animal bodies. Eight 
ninths of water and one half of the 
solid crust of the earth are oxygen 
in combination with other elements. 
Oxygen is also present in all animal 
and plant tissue, making up a large 
portion of the weight of these bodies. 
36. Preparation. — Oxygen can 
be prepared from a number of 
materials, as oxid of mercury and 
potassium chlorate. When made 
in small amounts in the laboratory, 
it is generally prepared by heating 
potassium chlorate, a compound 
composed of the elements potas- 
sium, chlorin, and oxygen. The 
oxygen is separated by means of 
heat, the process being as follows : 




Fig. 13. — Delivery tube. 



Experiment 1. — Fuse the end of a 
piece of glass tubing, 2\ or 3 feet long. 
Make a bend nearly at right angles to the 
tube, about 3 inches from one end. Then make a second bend of 2\ 
or 3 inches on the opposite end of the tube nearly at right angles, and 

30 



OXYGEN 



31 



in an opposite direction from the first bend (Fig. 13). Fit to the test 
tube a cork, as directed in Section 26, and insert the delivery tube. 
Fill the pneumatic trough nearly full of water, and place in it the 
free end of the delivery tube (Fig. 14). Weigh out 5 grams each of 
potassium chlorate (KC10 3 ) and manganese dioxid (Mn0 2 ). Mix 




Fig. 14. — Preparation of oxygen. Pneumatic trough. 



on a sheet of paper, and place the mixture in a test tube. See that 
the test tube is perfectly dry, both inside and out. Fill the cylin- 
ders with water, cover with glass plates, and place them inverted on 
the shelf of the pneumatic trough. With a medium-sized flame, 
apply heat cautiously to the test tube. The flame should be moved 
from time to time, and not allowed to strike just one part of the 
test tube, otherwise the glass will melt, and the test tube collapse. 
As soon as bubbles of gas are given off freely from the water, place 
the end of the delivery tube so that the gas is collected in one of the 
cylinders. When a cylinder is filled, cover it with a glass plate, 
while the mouth of the cylinder is still under water. The cylinder 
can then be placed upright upon the desk, and another filled with O. 
After collecting three or four cylinders of gas, remove the end of 
the delivery tube from the water, and then remove the flame. Do 
not remove the flame while the end of the delivery tube is under 
water, or a vacuum will be formed, and the water will rush back 
into the test tube. Tests should be made with O as follows : 

(1) Light a splinter and place it for a moment in one of the cylin- 
ders of oxygen (see Fig. 15) ; remove it; extinguish the flame, and 
while the splinter is still glowing, thrust it again into the cylinder. 
Observe the result in each case. (2) Put a small piece of sulfur, 
a little larger than a grain of wheat, into the iron or deflagration 



3 2 



AGRICULTURAL CHEMISTRY 



spoon ; ignite in the flame, and thrust into the second cylinder of 
O. Observe the result. (3) Take a piece of bright fine iron wire 
or watch-spring, and make it into a spiral with a loop at one end. 

Warm the wire by holding it near the 
flame, then hold the loop for an in- 
stant in the flame and dip it into some 
sulfur which has been placed on a piece 
of paper. Hold again in the flame for a 
moment and then place at once in the 
third cylinder of O. In order to insure 
the success of this experiment, the wire 
should be very fine, free from rust, and 
held in the flame only long enough to 
start ignition, and then placed in the 
cylinder. 

Questions. — (1) Where does the in the 
cylinder come from? (2) What caused it 
to separate from the compound ? (3) What 
is the appearance of O ? (4) Compared 
with air, is it a light or a heavy gas ? 
(5) What caused the splinter to burn and 
to rekindle ? (6) What product was formed when the splinter was 
burned? (7) What caused the sulfur to burn ? (8) What product was 




Fig. 15. — Testing oxygen 
with burning splinter. 




Fig. 16. — Preparation of oxygen, using sink in place of pneumatic trough. 

formed when the S was burned ? (9) Why do these materials burn 
differently in than in air ? (10) What caused the iron to burn, and 



OXYGEN 33 

what was formed ? (n) Is O combustible ? (12) Is O a supporter 
of combustion ? (13) What compounds are always formed by the 
union of O with an element? (14) Give the properties and char- 
acteristics of O as observed from this experiment. 

The oxygen in potassium chlorate is not held in firm chemical 
combination, and when the substance is heated, first a part, and 
finally all, of the oxygen is given off. Manganese dioxid is used 
because of its physical action upon potassium chlorate, enabling the 
oxygen to be given off more easily. The change which takes place 
is expressed by the equation : KC10 3 = KC1 + 3 O. The products 
of the reaction are potassium chlorid and oxygen. The oxygen is 
collected in the cylinders, while the potassium chlorid remains with 
the manganese dioxid in the test tube. 

37. Properties of Oxygen. — Physically considered, 
oxygen is a colorless, odorless, and tasteless gas, about 
16 times as heavy as hydrogen. It is slightly soluble in 
water, and, when subjected to low temperature and 
high pressure, it is liquefied. Chemically, oxygen unites 
with all common elements to form oxids. It is not com- 
bustible, but is a supporter of combustion. When the 
burning splinter was thrust into the cylinder of oxygen, 
the carbon and hydrogen of the wood united with the 
oxygen in the cylinder, forming carbon dioxid and water. 
When substances unite with oxygen they are oxidized; 
that is, oxygen is added to the material. An oxid is a 
compound of oxygen and any other element. When sul- 
fur is burned, it unites with oxygen, forming sulfur dioxid, 
S0 2 . Other elements, as phosphorus and iron, also 
unite with oxygen, forming oxids. Different elements 
unite with oxygen at different temperatures. Phosphorus 
and sulfur combine with oxygen at a comparatively low 
temperature, while carbon and iron require a higher 
temperature. The sulfur and the splinter of wood burned 
more brilliantly in the oxygen than in the air because air 



34 AGRICULTURAL CHEMISTRY 

is diluted with other gases and elements and is not pure 
oxygen. Oxygen is more active at a high than at a low 
temperature. 

Oxidation of some of the elements and compounds 
results in the production of light and heat, and this is 
commonly called combustion, although it does not 
necessarily follow that when a substance contains oxygen 
it is combustible, because it may be the product of com- 
bustion, as carbon dioxid or sulfur dioxid. Oxygen forms 
stable compounds with many of the elements. It has 
such affinity for some elements, as aluminum and carbon, 
that it is separated from them with difficulty. With 
other elements it forms less stable compounds. When an 
element, as oxygen, enters into chemical combination, it 
loses its identity or individuality as an element. The 
oxygen in the minerals forming the crust of the earth, 
and in plant and animal tissues, is not free, but combined 
with other elements. 

38. Importance. — Oxygen takes an important part in 
life affairs, and is necessary to the existence of plant and 
animal bodies. The combustion of wood, coal, and other 
fuel is due to the oxygen of the air. The production of 
heat in the body is due to oxidation of food, and many 
of the chemical changes which take place in the soil are 
dependent upon this element. Because of its wide distri- 
bution in nature, it is not given such economic considera- 
tion as are other elements, but it is one of the most im- 
portant, and is as necessary for life as other food. 

Problem 1. — How many pounds of oxygen are required to com- 
bine with 25 pounds of pure carbon ? When carbon is burned, 1 
part of C (called an atom) unites with 2 parts of O (2 atoms of O) 
to form the compound C0 2 . This is expressed by the equation 
C + 2 O = C0 2 . The atomic or least combining weight of carbon 



OXYGEN 35 

is 1 2 and of O is 16 ; one part by weight of C weighing 1 2 unites with 

2 parts by weight of O, each part weighing 16; or 12 parts by 

weight of C unite with 32 parts by weight of O. If the parts are 

designated pounds, then 25 pounds of C will require proportionally 

as much O as do 12 pounds of C. This amount can be determined 

by a simple proportion. 

C:0::C:0 

12 : 32 : : 25 : x 
By solving this proportion, x, or the required amount of O to com- 
bine with 25 pounds of C, is found to be 66f . 



In the solving of chemical problems some of the most 
common errors are: (1) Failure to write properly the 
formulas of the compounds used, or the equation repre- 
senting the chemical reaction that takes place. This 
error causes the wrong number of parts of elements or 
compounds to be taken in the proportion. (2) Failure 
to make proper use of the combining weights of the ele- 
ments. (3) Failure to combine properly the weights so 
as to form a true proportion. It should be remembered 
that after the writing of the equation and weights, the 
problem becomes simply one of arithmetic. 

Problem 2. — How many pounds of C0 2 are produced when 25 
pounds of carbon are burned ? 

Problem 3. — How many pounds of carbon are necessary to com- 
bine with 25 pounds of O in forming C0 2 ? 



CHAPTER V 
Hydrogen 

39. Occurrence. — Hydrogen is found in nature in com- 
bination with other elements, entering into the composi- 
tion of water, animal and plant tissues, and some min- 
erals. It is never in a free state, except as given off in 
traces with volcanic gases. Hydrogen is an essential 
part of all acids and of many other compounds. 

40. Preparation. — In the laboratory, hydrogen is 
usually prepared by treating a metal with an acid which 
contains hydrogen ; the metal replaces the hydrogen of 
the acid, and the hydrogen is then liberated as a free gas. 
When zinc and hydrochloric acid are employed, the reac- 
tion which takes place is as follows : Zn + 2 HC1 = 
ZnCl 2 + 2 H. Two molecules of hydrochloric acid are 
required in the reaction because zinc has a valence of 2 
and whenever zinc enters into chemical combination, it 
must take the place of two monovalent atoms. The 
compound, ZnCl 2 , zinc chlorid, contains one atom of zinc 
and two atoms of chlorin. 

Experiment 2. — Arrange the apparatus as shown in Fig. 17. 
Use a small two-necked Woulff bottle, and in one of the necks in- 
sert a tight-fitting cork with a thistle tube. In the other neck insert 
a cork carrying a delivery tube. Place about 20 grams of zinc, Zn, 
and 25 cc. of water in the Woulff bottle. The thistle tube should 
pass below the surface of the water to prevent the escape of gas. 
Fill two or three cylinders with water for collecting the gas. The 
corks carrying the delivery tube and the thistle tube should fit 
tightly, otherwise the H is easily lost. When all is ready, add, 

36 



HYDROGEN 



37 



through the thistle tube, about 15 cc. concentrated hydrochloric 
acid (HC1), and then sufficient water to carry the acid out of the 
trap of the thistle tube. Do not apply any heat whatever. Do not 
collect any gas until the generator has been going for about two minutes, 
and do not attempt to light the gas as it issues from the generator. Col- 
lect one or two cylinders of gas, adding more acid if necessary, 
always keeping the cylinders covered, mouth downward, because 




Fig. 17. — Apparatus for preparation of hydrogen. 

H is a light gas, and will readily escape if the cylinders are placed 
right side up. 

When working with hydrogen in the laboratory, the 
student should always exercise care, because mixtures of 
hydrogen and oxygen are very explosive. Only a spark or 
a near-by flame is necessary to bring about an explosion. 

Make the following test with hydrogen : Thrust a burn- 
ing splinter into the mouth of the cylinder of hydrogen, 
as shown in Fig. 18. 

Questions. — (1) What is the color of H? (2) Odor? (3) Is it 
a light or heavy gas ? (4) Does it support combustion ? (5) Is it 
combustible ? (6) What is formed when H is burned ? (7) How 
do you know that this product is formed ? (8) From what com- 



38 



AGRICULTURAL CHEMISTRY 



pound was the H obtained ? (9) What caused the H to be liberated 
from this compound? (10) Why are mixtures of H and O very- 
explosive ? (11) What other acids could be used in the preparation 
of H ? (12) What other metals could be used in the preparation of 
H ? (13) Give the equation for the reaction of Zn and HC1. 
(14) What do these tests prove in regard to the character and 
properties of the element H ? 




Fig. 18. — Thrusting burning splinter into hydrogen. 



41. Properties. — Physically, hydrogen is characterized 
as a colorless, odorless, and tasteless gas. It is the 
lightest in weight of any of the elements, and for that 
reason is taken as the standard for the atomic weights. 
At a low temperature, and under pressure, hydrogen can 
be liquefied, with greater difficulty, however, than any 
other element. Hydrogen is 14.43 times lighter than air. 
A liter of hydrogen, under standard conditions of tempera- 
ture and pressure, weighs 0.08961 gram. Chemically, 



HYDROGEN 



39 



hydrogen is characterized as combustible, but not a sup- 
porter of combustion. It readily combines with many 
other elements, particularly oxygen, with which it forms 
water. When hydrogen and oxygen unite to form water, 
a reaction takes place which causes a contraction in vol- 
ume. Two volumes of hydrogen and one volume of oxy- 
gen unite to produce two volumes of water 
vapor or steam. When hydrogen and oxygen 
unite, there is always an explosion, due to 
contraction in volume. That water is pro- 
duced when hydrogen is burned, can be dem- 
onstrated by placing a dry test tube over a 

flame of hydrogen. The 
interior of the test tube 
will become covered 
with moisture. Hydro- 
gen does not unite with 
all elements as readily 
as does oxygen. When 
hydrogen is burned, the 
flame is nearly colorless 

Fig. io. — Preparation of hydrogen, using a because Combustion is 

wide-mouthed bottle and sink in place of com plete, and there are 

a Woulff bottle and pneumatic trough. 

in the flame no solid 
particles heated to incandescence. Hydrogen produces a 
very hot flame, and, when mixed with oxygen in the right 
proportion, as in the oxyhydrogen blowpipe, a high tem- 
perature is secured. 

42. Importance. — Hydrogen is one of the essential 
elements for the formation of compounds in plant and 
animal tissues, but because of its extreme lightness it 
never makes up a large portion by weight of a material. 
As a free element, it takes no part in life processes, but 




4° AGRICULTURAL CHEMISTRY 

when combined with water, and in other forms, as in 
food materials where it is united with carbon and oxygen, 
it is an essential part of compounds which are of much 
importance for animal and plant life. 

Problem i. — How many pounds of H will ioo pounds of Zn 
liberate when it is acted upon by H 2 S0 4 ? 

Problem 2. — How much ZnCl 2 is formed when 100 pounds of 
Zn are acted upon by HC1 ? 



CHAPTER VI 
Nitrogen 

43. Occurrence. — Nitrogen occurs abundantly in a free 
state in the air, nearly 23 per cent by weight being uncom- 
bined nitrogen. It also forms a part of some of the com- 
pounds which make up animal and plant tissues, where 
it is in chemical combination with carbon, hydrogen, and 
oxygen. Nitrogen is present also in the soil, forming a 
part of the decaying organic matter. It is one of the ele- 
ments of ammonia gas and ammonium compounds, and is 
in combination with other elements, as in nitrates. 

44. Preparation. — Nitrogen is usually prepared from 
air by removing the oxygen with which it forms a me- 
chanical mixture. Since air is composed of both oxygen 
and nitrogen, if the oxygen in a given volume of air, as 
in a cylinder, is chemically united with phosphorus or 
carbon, forming soluble products, there is a residue of 
nitrogen left in the cylinder. Nitrogen produced in this 
way is not pure, but contains traces of other elements and 
compounds. For experimental purposes, it may, how- 
ever, be considered nitrogen. Nitrogen can also be 
produced from its compounds, as by the removal of the 
hydrogen from ammonia gas. The method of prepara- 
tion in the laboratory is as follows : 

Experiment 3. — Insert a long pin through the center of a large 
flat cork. Fasten a short piece of candle to the cork by means of 
the pin. Nearly fill the pneumatic trough with water. Light the 
candle and float it upon the surface of the water. Invert a large 
cylinder over the candle, having the mouth of the cylinder just 

4i 



42 



AGRICULTURAL CHEMISTRY 



below the surface of the water, as shown in Fig. 20. After the 
candle is extinguished, remove it with the hand, reaching through 
the water into the cylinder without admitting any air. While the 
cylinder is still under water, cover it with a glass plate and remove 
from the trough. Then make the following tests : 

(1) Insert a burning splinter into the cylinder of N. Observe 
the result. (2) Place a little sulfur in the deflagration spoon, ignite, 
and insert in the cylinder of N. Observe the result. (3) With a 




Fig. 20. — Preparation of nitrogen. 



ruler, measure the height of the cylinder and the amount of water 
left in the cylinder. 

Questions. — (1) What is the color of N ? (2) Odor? (3) Com- 
pared with air is it a heavy or a light gas ? (4) Is it combustible ? 
(5) Does N support combustion ? (6) Is N an active element ? 
(7) What portion of the cylinder is filled with water in the prepa- 
ration of N ? (8) What portion of the cylinder is filled with N ? 
(9) What portion of the cylinder did the O occupy? (10) What 
becomes of the products of combustion of the candle? (11) What 
do these experiments prove in regard to the element N ? (12) Com- 
plete the following table : 



Color. Taste. Combus- Supporter of 



Where 
found. 



Name of Svmbol Combin- 

element. y * ing wt. »-«"»■ tible. combustion. 

Oxygen 

Nitrogen 

Hydrogen 

When the candle is burned, the oxygen of the air in the cylinder 
unites with the carbon and hydrogen from the candle and forms 



NITROGEN 43 

carbon dioxid and water. The C0 2 is soluble in water, and the gas 
that is left is mainly nitrogen. The combination of the oxygen 
with the carbon causes a partial vacuum to form, and this results 
in the water rising in the cylinder. If great care is taken in per- 
forming the experiment, it will be found that the water fills about 
one fifth of the cylinder, occupying the space of the oxygen which 
has been combined with the carbon. When all of the oxygen in 
the cylinder is combined with the carbon, the candle is extinguished 
because of lack of oxygen for 'combustion. 

45. Properties of Nitrogen. — In general, the physical 
properties of nitrogen, except weight, are somewhat like 
those of hydrogen and oxygen, inasmuch as when pure, 
it is colorless, tasteless, and odorless. It is about 14 
times as heavy as hydrogen, and only slightly soluble in 
water. At a low temperature and under pressure, it is 
liquefied, and at a still lower temperature and under higher 
pressure, it is solidified. 

Chemically, nitrogen is unlike either hydrogen or oxy- 
gen. It is an inactive gas ; it is neither combustible nor 
a supporter of combustion. When in the free state, it is 
one of the most inactive of all the elements, and will com- 
bine directly with only a few. When nitrogen enters into 
combination with other elements, particularly with carbon 
and hydrogen, forming the organic compounds, it has 
a tendency to make a weak link in the combination, 
and will readily split off to form simpler products. In 
the air, it serves the purpose of diluting the oxygen. No 
other element could perform this function so well as 
nitrogen. If the air were composed of pure oxygen, all 
combustion would be carried on in a rapid and wasteful 
manner. Nitrogen is not a poisonous gas, but if an animal 
were compelled to breathe pure nitrogen, it would die 
for need of oxygen. Some of the compounds of nitrogen 
decompose with violence, causing explosions. Nearly 



44 AGRICULTURAL CHEMISTRY 

all the explosives, as gunpowder, nitroglycerin, and gun- 
cotton, are compounds of nitrogen. 

46. Importance. — The compounds of nitrogen take an 
important part in animal and plant life. In combination 
with carbon, hydrogen, and other elements, nitrogen forms 
the nitrogenous compounds of plant and animal bodies. 
These compounds are called organic nitrogenous compounds 
because they are capable of undergoing combustion, and 
they produce volatile and gaseous products when burned. 

In the study of foods, and of soils and fertilizers, the 
element nitrogen is given a prominent place. This is 
because it is one of the most expensive elements in com- 
mercial fertilizers, and foods which contain nitrogenous 
compounds are the most expensive. Although nitrogen 
is found uncombined in the air, it is made use of as a 
plant food by only a limited number of plants, and then 
in an indirect way. Nitrogen forms a large number of 
important compounds, as ammonia, nitrates, nitrites, 
amids, and the complex organic compounds, proteids. 
Some of these will be studied more in detail in future 
chapters. To the agricultural student, nitrogen is one 
of the most important elements because of the role which 
it plays in plant and animal economy. 

Problem 1. — Calculate the per cent of N in NaNC>3. 
Problem 2. — Calculate the per cent of N in NH 3 . 
Problem 3. — Calculate the per cent of N in (NH^SO^ 



CHAPTER VII 
Carbon 

47. Occurrence. — Carbon is found in the free state 
in limited amounts only, but is mainly in combination 
with other elements. With the metals and oxygen, it 
forms carbonates, such as calcium carbonate or limestone. 
With hydrogen and oxygen, and a few other elements, 
it forms a large number of compounds of which plant and 
animal tissues are composed. All substances which 
char or blacken when burned contain carbon in combi- 
nation. Diamonds, coal, and graphite are forms of this 
element in various degrees of purity. With oxygen, it 
is present in the air in small amounts as carbon dioxid. 
About half of the dry substance of wood and animal 
tissue is carbon. It occurs in nature in a great variety 
of forms. 

48. Preparation. — In the form of charcoal, carbon 
can be prepared from wood, by application of heat in 
the absence of air or oxygen, when a change known as 
destructive distillation takes place. The hydrogen, oxy- 
gen, and nitrogen of the wood are expelled, and a black 
mass of impure carbon and mineral matter is left. To 
make charcoal, wood is piled and burned in suitable pits, 
which, after the combustion is well started, are covered 
with turf to protect the burning mass from the air. Char- 
coal can be produced on a small scale in the laboratory, 
in the following manner : 

45 



4 6 



AGRICULTURAL CHEMISTRY 



Experiment 4. — Place two or three small pieces of wood in a 
Hessian crucible, and cover with sand. Heat the crucible until 
smoking ceases (see Fig. 21). Remove and examine the charcoal. 
Questions. — (1) What are the principal elements in wood? 
(2) What becomes of these various elements when the material is 
heated ? (3 ) Why was sand used in this exper- 
iment ? (4) What becomes of the ash or mineral 
matter in the process of charcoal making ? (5) 
What is charcoal, and of what element is it prin- 
cipally composed ? (6) Does charcoal have a crys- 
talline structure ? (7) What would be the result 
if sand were not used in the experiment ? (8) 
Give the equation for the combustion of carbon. 
(9) How can charcoal be made on a large scale ? 

Particles of carbon may also be obtained from 
a gas, candle, or lamp flame, by holding a piece 
of cold porcelain a little above the flame. Carbon, 
in the form of soot, is deposited in chimneys when 
fuel is burned with a poor draft. When combus- 
tion is complete, the carbon is oxidized, forming 
carbon dioxid. If a fire gives off a large amount 
of dense black smoke, the carbon is not com- 
pletely oxidized, and consequently there is a loss of fuel value. 




Fig. 21. — Prepara 
tion of charcoal 



49. Properties. — Carbon is found in three forms in 
nature : as diamond, graphite, and amorphous carbon. 
The diamond is a pure form of crystallized carbon. It 
can be burned like any other form of the element, and 
produces carbon dioxid. Diamonds of small size are 
produced artificially by the cooling of graphite from 
molten iron. Graphite also is a crystalline form of carbon, 
but the crystals are of different shape and color from 
diamond crystals. Graphite is soft, and is used extensively 
as a lubricant. As it does not burn as readily as other 
forms of carbon, it is used, too, for making crucibles and 
for the linings of furnaces. It is a natural product and 
also is produced artificially by dissolving carbon in iron. 



CARBON 47 

There are a great many uncrystallized or amorphous 
forms of carbon, as lignite and soft coal, lampblack, 
and charcoal. 

50. Coal. — All the conditions under which coal has 
been produced are not known. It is supposed to be the 
result of the joint action of heat and pressure upon pre- 
historic forms of vegetation. Hard or anthracite coal is 
the purest form known, and yields the least ash and 
unoxidized volatile products. Bituminous or soft coal 
is less pure, as more of the carbon is in chemical combina- 
tion with the other elements, and when burned, the carbon 
is not as completely oxidized under ordinary conditions 
as is that of hard coal. Coal may contain a number of 
impurities, as sulfur and mineral matter. Cannel coal 
is a variety which contains a large amount of mineral oils. 

Lignite is vegetable matter which has only partially 
undergone the coal-forming process. It is less pure than 
soft coal, and is supposed to be an intermediate stage 
in its formation. Peat is vegetable matter which has 
undergone chemical changes under water. It has a lower 
fuel value than lignite. 

51. Allotropism. — An element which has the power to 
take on so many different physical forms as has carbon 
is called an allotropic element. Only a few elements have 
the properties of allotropism. 

52. Carbon as a Reducing Agent. — Carbon is used 
extensively for the reduction of minerals. It unites with 
the oxygen of minerals and ores to form carbon dioxid. 
In the reduction of iron ore, the oxide of iron is heated 
with carbon in the form of coke. The ore is reduced 
by giving up its oxygen to the carbon. When reduc- 
tion takes place oxygen is removed by a reducing agent, 
while oxidation is the chemical union of oxygen 



4 8 



AGRICULTURAL CHEMISTRY 



\\4th a substance. The action of carbon as a reduc- 
ing agent may be observed from the following experi- 
ment : 

Experiment 5. — Mix thoroughly 2 or 3 grams of copper oxid 
# (CuO) and an equal bulk of charcoal (animal charcoal). Place the 
mixture in a small test tube and apply heat. Observe the result. 

Questions. — (1) What is the bright red material produced in the 
test tube ? (2) What was the source of this material ? (3) What 
caused the O to be separated from this compound ? (4) What did 
it unite with ? (5) What was formed as the product ? (6) Write 
the reaction. (7) Why is carbon called a reducing agent ? (8) What 
kind of an agent would CuO be called ? (9) Why is carbon useful 
in separating minerals from their ores ? 



^d&SLSUBgg 



53. Combustion. — Combustion, in the ordinary sense, 
is simply the union of carbon with oxygen, and, as a 
result, light and heat are given off. If the process is 
A slow, and heat without 

/ 1 light is evolved, it is 

^==znr~~ slow oxidation, and the 
total amount of heat 
generated is the same as 
if the material underwent direct combus- 
tion. An example of slow oxidation is the 
rusting of metals. The regulation of drafts 
in stoves to influence the combustion of 
fuel so as to obtain the largest amount of 
heat, is based upon the simple laws of the 
combustion of carbon. 

A candle or gas flame well illustrates the 
laws of combustion. The outer portion of the flame is a 
non -luminous envelope of gases undergoing perfect com- 
bustion ; within this is a layer of gases undergoing partial 
combustion, and constituting the light-giving part of the 




Fig. 22. — Com- 
bustion. 



CARBON 



49 



7 

A 




flame ; while in the center is a zone which is more perfectly 
cut off from the air, and little or no combustion is taking 
place. The combustion of a gas or candle flame may be 
studied from the following experiment : 

Experiment 6. — Structure of the flame. Unscrew the top of a 
Bunsen burner and make a drawing showing how the burner works, 

and the workings of the ori- 

•_^== ^ fices at the bottom of the 

burner. Replace the parts 
of the burner, open the air- 
holes at the base, and light the gas. Hold a sheet 
of paper back of the flame and try to distinguish 
the three parts: (i) the outer non-luminous en- 
velope of perfect combustion; (2) the inner lumi- 
nous zone of partial combustion ; (3) the central 
blue cone of unburned gas. Make a drawing of 
the flame. Press a piece of card board or paper 
down upon the flame for an instant and remove it 
before it takes fire. Observe the result. Hold a 
piece of wire close to the burner and observe that 
at first the wire does not become red at the center of the flame. 
Thrust the head of a match into the center of the flame for an in- 
stant and then remove it. If this is done quickly, the match can 
be removed before combustion takes place. Place a piece of wire 
gauze above the flame as shown in Fig. 23. Observe the result. 
Extinguish the gas. Hold the wire gauze about an inch above the 
burner, then light the gas above the gauze (Fig. 22). 

Questions. — (1) Why was a charred circle formed when the piece 
of paper was pressed down upon the flame ? (2) Why did the wire 
first redden near the outer portions of the flame and not at the 
center ? (3) Why did the flame refuse to burn above the wire gauze 
when the gauze was pressed down upon the flame ? (4) When the 
gas was lighted above the gauze, why did it refuse to burn below ? 
(5) What is kindling temperature ? (6) What are the three con- 
ditions necessary for combustion ? (7) What condition was lacking 
when the gauze was placed in the flame ? (8) Why does a flame 
give light when air is excluded from the burner, and give but little 
light when the air vent is open ? (9) Does the amount of light which 

E 



Fig. 23. — Com- 
bustion. 



50 AGRICULTURAL CHEMISTRY 

a flame produces indicate the amount of heat produced ? Why ? 
(10) What causes a flame to give light ? (n) Why do some mate- 
rials, when burned, produce more flame than others? (12) What 
is spontaneous combustion ? (13) Explain how it is possible for 
clover or fodder to undergo spontaneous combustion in a barn. 
(14) What can be done to prevent spontaneous combustion ? (15) 
Carbon, when burned, produces heat ; limestone, CaC0 3 , contains 
carbon ; why is it not possible to use limestone for fuel ? 

54. Spontaneous Combustion. — In order for a sub- 
stance to undergo combustion, it is not always necessary 
for a match or a flame to be applied to it. As soon as 
it is heated to its kindling temperature, that is, the tem- 
perature at which it unites with oxygen, if in the presence 
of air, combustion takes place, called spontaneous com- 
bustion. Clover, when stored in a damp condition, may 
undergo spontaneous combustion. The fermentation 
which takes place produces combustible gases which, 
at suitable temperature, ignite, and the 
burning gases, in turn, ignite the carbon 
of the material. Substances containing a 
great deal of oil and materials of low kindling 
temperature, as carbon bisulfid, phosphorus 
and sulfur, under suitable conditions of tem- 
perature and air, readily undergo SpOntan- 
FiG. 24 .-Candle eQUS com b US tion. 
flame. 3. Non- 
luminous cone. In case of fire, the laws governing com- 

4. Luminous fortiori should be taken advantage of. If 

line. 5,6. Outer . & 

non-luminous the fire is a small one, cut oft the supply of 
envelope. a i rj anc [ ^he -Q re [ s extinguished. This can be 

accomplished by the use of sand, wet blankets, or any 
material that will cut off the supply of air. In order 
for spontaneous combustion to take place, there must 
be (1) a combustible substance, which (2) is heated 




CARBON 



51 



to its kindling temperature, (3) in the presence of 
air. 

55. Carbon a Decolorizer and Deodorizer. — Wood and 
animal charcoal have the power of absorbing gases and 
coloring materials from solutions. In the manufacture 
of sugar, a part of the impurities are removed by bone- 
black or animal charcoal filters, and in purifying water, 
charcoal filters are often used. The power of carbon 
to abstract gases and coloring matter is largely a physical 
property. In the soil, the carbon compounds decay and 
produce humus, which has some of the power of charcoal 
to absorb gases and soluble bodies. 

Experiment 7. — Place in a cylinder 2 grams of animal charcoal 
and about 1 cc. cochineal solution diluted with 10 cc. water. Cover 
the cylinder with a glass plate and shake ; then pour the contents 
of the cylinder into a filter. If the first of the filtrate is not clear, 
pass it through the filter a second time. 

Repeat the experiment, using 2 cc. potassium 
sulfid solution, 2 cc. hydrochloric acid, and 10 cc. 
water in place of the dilute cochineal solution. 

Questions. — (1) What effect did the animal 
charcoal have upon the color of the solution ? 
(2) What property of animal charcoal does this 
show ? (3) What was the result of filtering the 
potassium sulfid solution ? (4) What property of 
animal charcoal does this show ? 



56. Products of Combustion. — The 

carbon dioxid gas given off from either 
a candle or a gas flame can be col- 
lected by arranging an apparatus like 
that shown in Fig. 25. A metal funnel 
is connected with a delivery tube which 
passes near the surface of a solution of lime water, 
Ca(OH) 2 , in a test tube. The carbon dioxid given 




Fig. 25. — Collecting 
carbon dioxid from 
candle. 



52 



AGRICULTURAL CHEMISTRY 




Fig. 26. — Obtaining unburned 
gas from candle. 



off from the flame passes into the lime water, and, by form- 
ing calcium carbonate, causes it to become cloudy. 
Ca(OH) 2 + C0 2 = CaC0 3 + H 2 0. The carbon comes 

from the gas, which under- 
goes combustion, and is com- 
bined with hydrogen as hydro- 
carbons. That a candle pro- 
duces its own combustible 
gases can be proved by collect- 
ing some of the gas with a 
glass tube and rubber bulb as 
shown in Fig. 26. This gas 
can then be burned as in- 
dicated in Fig. 27. The hy- 
drogen of gas or a candle 
forms H 2 during combustion, 
and can be collected by passing the products of combus- 
tion through suitable absorbents. If a dry 
test tube is held above the flame, a little mois- 
ture will collect on the sides of the test tube. 
57. Compounds of Carbon. — Chemi- 
cally, carbon forms a very large number of 
compounds, more, in fact, than any other 
element. The carbon compounds in plant 
and animal tissues are studied in a divi- 
sion of chemistry known as organic 
chemistry, while those compounds of car- 
bon which are in combination with the 
mineral elements, as calcium, sodium, and 
potassium, are studied in a division termed 
inorganic chemistry. No well-defined bound- 
ary line, however, can be established between these 
two divisions of chemistry. 




Fig. 27. — Com- 
bustion of gas 
from candle. 



CARBON 53 

58. Importance of Carbon. — The carbon compounds 
take a very important part in animal and plant growth. 
And commercially, they are of great importance, as they 
are found in foods, fuels, and in all animal and plant 
products. Carbon is present in plant and animal bodies 
in larger amounts than any other element. Carbon is the 
element essential for the production of heat when fuels 
and foods are oxidized. 

Carbon is in the air in the form of carbon dioxid in 
sufficient amounts for the production of crops. It is 
also in human and animal foods in large amounts ; but 
because of its abundance, and its distribution in balanced 
form, it has not been considered of so much importance 
economically in the production of plants as nitrogen. 
It is, however, equally important, although its natural 
distribution is such that it does not require so much 
effort, on the part of man, to obtain it as it does other 
forms of plant food materials. Nevertheless, the carbon 
compounds, particularly in food materials, should not 
be disregarded or considered of little or no importance 
because of their abundance. In studying foods and soils 
and fertilizers the student will find some of the compounds 
of carbon considered more in detail. 



CHAPTER VIII 
Water 



59. Chemical Composition. — That water is composed 
of hydrogen and oxygen in approximately the proportion 
of 2 volumes of H to 1 of O can be demonstrated by pass- 
ing a current of electricity through water 
and collecting the escaping gases. Oxy- 
gen is liberated at the positive electrode, 
while hydrogen is liberated at the nega- 
tive electrode. That water is composed 
of 16 parts, by weight, of oxygen, to 2 
parts, by weight, of hydrogen, can be 
demonstrated by passing hydrogen gas 
over copper oxid heated in a tube. The 
reaction which takes place is CuO + 
2 H = H 2 + Cu. If suitable provisions 
are made for weighing the oxid of copper 
used, and the water produced, it will be 
found that the weight of the water 
bears definite relation to the amount of oxid of copper 
reduced. For every loss of 16 grams of oxygen from 
the copper oxid, 18 grams of water are obtained, showing 
that water is eight ninths, by weight, oxygen. 




Fig. 28. — Electrol- 
ysis of water. 



Experiment 8. — Distillation of water. Connect flask A (Fig. 
29) with the bent tube B to the condensing apparatus issued for 
this experiment. Place the distilling flask upon the sand bath and 
in position as shown in Fig. 29. Fill the tank of the distilling 
apparatus, and half fill the flask, with water. Apply heat to the 

54 



WATER 



55 



flask, and reject the first portion of water that is distilled. Distil 
about 25 or 30 cc. of water. 

Tests. — (1) Thoroughly clean your porcelain evaporating dish, 
if necessary using a little white sand for scouring, rinse with dis- 
tilled water, and then by 
placing the evaporator upon 
a sand bath, evaporate some 
of the distilled water to 
dryness. Carefully regulate 
the heat so that as the water 
evaporates there will be less 
and less heat. This is to 
prevent the breaking of the 
evaporating dish by too 
much heat at the close. 
Examine the evaporating 
dish. See if there is any 
residue. (2) Evaporate to 
dryness a similar amount of 
ordinary water, and observe 
the residue 

Questions. — (1) Why do the contents of flask A become cloudy 
after boiling and cooling? (2) Why was the residue obtained by 
one test and not by the other? (3) What became of the residue 
when the water was distilled ? (4) How could you distil water on 
a larger scale for drinking purposes, if necessary to do so ? 




Fig. 29. — Distillation of water. 



60. Physical Properties. — When water cools, it 
reaches its maximum density at 4 C. ; below this point, 
it expands, and hence ice has a lower specific gravity 
than water. All natural waters contain more or less im- 
purities in the form of mineral and vegetable matter and 
gases. Pure water can be prepared only by distillation. 
When a substance, as salt, is dissolved in water, a solu- 
tion is obtained. The particles of the material are sepa- 
rated in the process of solution, and every part of the 
solution, even though dilute, contains some of the dis- 



56 AGRICULTURAL CHEMISTRY 

solved substance. When a substance is dissolved, ions 
are produced. They are small parts of the material that 
have undergone changes due to the action of the solvent. 
The ions possess definite electrical properties. When a 
substance goes into solution, the process is both physical 
and chemical. In some cases a change of temperature 
occurs, as when ammonium nitrate solution is made. 

61. Water of Crystallization. — Many substances con- 
tain, in chemical combination, water necessary for the 
formation of crystals. This is what is meant by water 
of crystallization. Without this water, crystals could 
not be formed. The amount of water required bears a 
definite relation to the composition of the crystals. When 
copper sulfate crystallizes, 7 molecules of water of crys- 
tallization are added to the substance. In purchasing 
some materials, as sulfate of soda, there is a large amount 
of water included, as this compound contains 10 molecules 
of water of crystallization. When the substance is heated 
in an oven to a sufficiently high temperature, usually 
above ioo° C, the water of crystallization is expelled and 
the anhydrous substance is obtained. Water of crystal- 
lization is entirely different from hydroscopic moisture 
or moisture absorbed from the air. Some chemical 
compounds, when exposed to the air, give up their water of 
crystallization. This is called efflorescence. Other com- 
pounds, as KOH and CaCl 2 , absorb moisture from the 
air. Such substances are called deliquescent. Water 
takes an important part in chemical reactions ; in fact, 
many of the reactions expressed in the form of equations 
could not take place without the presence of water. 

62. Natural Waters. — Rain, spring, lake, river, and 
sea waters are some of the principal forms in which water 
is found in nature. Some waters contain enough dissolved 




WATER 57 

salts to give them definite characteristics and are known 
as mineral waters. The most common impurities in 
water are lime, magnesia, potash, soda, and iron com- 
pounds. These substances give prop- 
erties to the water which cause them 
to be characterized as hard or soft, 
according to the nature and amount of 
minerals dissolved. All natural waters 
are liable to contamination, and the 
organic impurities serve as food for 
disease-producing organisms. The Fig. 30. — Typhoid 
sanitary condition of the water supply 
has an important bearing upon health. Typhoid fever, 
cholera, and other bacterial diseases are frequently 
caused by poor drinking water. The spores of the 
organisms present in the water are taken into the 
body, where they rapidly multiply. Surface wells, par- 
ticularly when near barns and dwellings, and in thickly 
settled regions, are frequently in an unsanitary condition. 
63. Impurities in Water. — The nature of the impuri- 
ties in the soil through which water flows determines the 
kinds of impurities in the water. If a soil is polluted 
with decaying animal and vegetable refuse matter, the sol- 
uble portions of these, along with the countless organisms 
which they contain, become a part of the drinking water. 
The impurities in well waters are (1) organic matter and 
(2) mineral salts. When water is charged with an exces- 
sive amount of organic matter, the solids obtained by 
evaporating the water to dryness blacken when ignited. 
The carbon compounds in a liter of some waters require 
20 mgs. or more of oxygen for oxidation. The organic 
matter may decompose and become harmless, but it is liable, 
in times of epidemics, to furnish food for disease germs. 



58 



AGRICULTURAL CHEMISTRY 



Water that is comparatively free from organic matter 
is not nearly so apt to convey disease germs as one that 
contains a large amount of such material, as this is the 
best kind of food for the development of the germs which 
cause many of the most fatal diseases. Vegetable matter, 
as a rule, is not as harmful in a water as animal matter. 
The organic refuse dissolved in waters is constantly 
decaying, and this decomposition is the result of the 
workings of minute organisms known as bacteria, which 
may be the disease-producing ones as well as the harmless 
kinds. The history of the water supply of large cities 
shows that a water which is comparatively free from 
organic matter is the best for household purposes. The 
source of the nitrogenous organic matter in drinking 
waters is often sewage or surface drainage, as from a 
swamp. Deep well waters are less liable to be contami- 
nated than surface wells, but a deep well is not above 




Fig. 31. — Well contaminated with drainage from swamp. 

suspicion, because the layers of soil are subject to changes 
in slope, and the water from a deep well may receive 
surface drainage from some distant place, as indicated in 
the illustration (Fig. 31). Although the soil would remove 
a portion of the impurities and the organic matter would 
be partially oxidized, the water would not be entirely 
free from contamination. 

64. Location of Wells. — Wells should be remote 



WATER 



59 



from barns and cesspools. Large trees about wells are 
objectionable because the water is fouled by waste matter 
thrown off by the roots. The top of the well for 6 or 8 




Fig. 32. — Construction of well. 



feet should be laid with cement. The well platform 
should be tight so that small animals are kept out. 
Drain water from the spout should be carried away from 



6o 



AGRICULTURAL CHEMISTRY 







SAND 



iLUAILJi II UU LU ' ^ I" niiiiiiiiiiimuuumumw 



-RESERVOIR- 






the well platform, and the watering trough should not be 
directly over the well. The land should slope away from 
the well and the surfacing should be of clay. The well 
- should have ventilation, and 

should occasionally receive a 
cleaning. 

65. Mineral Impurities. — Cal- 
cium carbonate, calcium sulfate, 
sodium chlorid, and sodium sul- 
fate are the most common min- 
erals present in water. In alkali 
waters the mineral impurities are 
sodium or potassium compounds, 
often in large amounts, and there 
is no way of improving such 
waters except by distillation. 
Different kinds of minerals, if 
in excessive amounts, may impart medicinal properties ; 
magnesium sulfate (Epsom salts) acts as a purga- 
tive, while calcium sulfate causes costiveness. Strong 
alkaline waters can generally be detected by their 
salty taste. An excess of some forms 
of alkaline salts in waters renders them 
unsafe for irrigation purposes, as the salts 
are destructive to plant life. 

Limestone in waters is not so serious as 
are other minerals. Waters sometimes con- 
tain limestone to such an extent that when 
boiled they become cloudy, which is be- 
cause of the removal of the carbonic acid 
gas which causes the limestone to remain in solution. 
Some waters that contain limestone are not considered in- 
jurious to health, although they are not so satisfactory for 



Fig. ss. — Charcoal water filter. 






==2?^ 



Fig. 34. — Un- 
glazed porcelain 
filter. 



WATER 



6l 



cleaning purposes because the lime acts upon the soap and 
forms a scum of insoluble lime soap. A large amount of 
limestone, gypsum, etc., causes waters to be hard. Some 
waters contain iron compounds, as carbonate of iron 
which, upon contact with the air, forms hydrate of iron, 
and is deposited as a brownish red sediment. Sometimes 
there is so much mineral matter in waters that when 
used for generating steam they produce a large amount 
of boiler scale. This can often be partially prevented 
by the use of materials as 
trisodium phosphate, soda 
ash and graphite, which 
form a sludge instead of a 
hard scale. 

66. Methods of Improv- 
ing Drinking Waters. — 
(i) By boiling, which de- 
stroys disease-producing 
organisms. Boiled or steril- 
ized water, however, is not 
free from the poisonous 
compounds which many 
organisms produce. In 
cases of pestilential dis- 
eases, water should always 
be boiled. 

(2) By filtering through 
charcoal or through disks 
of unglazed porcelain-like 
material, which results in 
removing a large part of the organic matter. Special care, 
however, should be taken to keep the filter clean, otherwise 
it will be a source of contamination. Boiling the water 




Fig. 35. — Pasteur water filter. 



62 AGRICULTURAL CHEMISTRY 

before filtering also improves its sanitary condition. One 
of the most efficient forms of water filters is the Pasteur 
filter, where the water passes through a series of tubes 
which present a large surface area for filtering. 

(3) By distilling, which removes all mineral impurities, 
and also purifies the water from organic matter. It is 
the best way of removing all kinds of impurities and 
rendering the water free from organisms, and safe for use. 

Chemical precipitation and filtration plants are often 
used for improvement of the water supply of cities. The 
suspended matter along with the dissolved organic im- 
purities are coagulated and precipitated by small amounts 
of iron and aluminum compounds, then enough lime or 
other substance is added to precipitate the excess of 
iron or aluminum salts. After precipitation the impur- 
ities are removed by filtration. Such plants are under 
supervision of chemists, and the reagents used vary with 
the amount and nature of the impurities contained in 
the water. Water of high sanitary quality can be secured 
by chemical precipitation and filtration methods. 



CHAPTER IX 
Air 

67. Air a Mechanical Mixture. — Air is a mechanical 
mixture of a number of gases and compounds in about 
the following proportions: (1) nitrogen, 79 per cent; 
(2) oxygen, 20 per cent ; (3) carbon dioxid, 0.04 per cent ; 
(4) ammonium compounds in small amounts; (5) mois- 
ture; (6) ozone; (7) hydrogen peroxici ; (8) argon; 
(9) dust, organic matter, and microorganisms. That 
air is a mechanical mixture is shown by its not having 
a constant chemical composition, which is necessary 
for all compounds, and when nitrogen and oxygen are 
mixed in the same proportion as in air, there is no evi- 
dence of a chemical reaction, as change of volume or 
temperature. The air that is dissolved in water is of 
different composition from atmospheric air, due to the 
fact that oxygen is more soluble in water than is nitrogen. 
The occurrence of nitrogen and oxygen in the air, and the 
chemical and physical properties of these gases, have 
been discussed in Chapters IV and V. 

68. Carbon Dioxid. — The amount of carbon dioxid 
in the air is small, about 0.04 per cent, and it is sup- 
posed to remain fairly constant. It is produced from : 

(1) combustion of carbon-containing materials, as fuels ; 

(2) decaying of organic matter ; and (3) respiration of 
animals. The carbon dioxid of the air serves as food 
for plants and is used for the construction of plant tissue. 
The amount produced and that used by vegetation 

63 



64 AGRICULTURAL CHEMISTRY 

nearly balance each other, so that the carbon dioxid 
in the air remains fairly constant. While the percentage 
amount in the air is small, the total amount is quite 
large ; it is estimated that over each acre of the earth's 
surface there are about 30 tons of carbon dioxid at the 
disposal of plant bodies. Carbon dioxid itself is not 
such a poisonous gas, but it is usually associated in 




Fig. 36. — Ventilating board in window for obtaining fresh air. 

respired air with noxious and poisonous products thrown 
off by the lungs. Hence the carbon dioxid in a room is 
taken as the index of the completeness of ventilation, and 
when it exceeds 0.1 per cent, the poisonous products 
associated with it are considered to be too much for 
sanitary conditions. While carbon dioxid is a product 
of respiration, and is of no direct economic importance 



AIR 65 

to animals, it is indirectly of great importance because 
of its serving as food for plants. It is a heavy gas, but 
in a room it diffuses and is quite evenly distributed. Its 
presence in pure and in respired air can be shown by the 
following experiment : 

Experiment g. — Pour 10 cc. of lime water (calcium hydrate) 
into a test tube, and blow through it, using for the purpose a clean 
glass tube. Observe the precipitate of calcium carbonate. Expose 
about 10 cc. of lime water in a beaker for twenty-four hours, and 
observe the result. The reaction which takes place between the 
lime water and the carbon dioxid of the air is as follows : 
Ca(OH) 2 + C0 2 = CaC0 3 + H 2 0. 

Questions. • — (1) What caused the precipitate to form ? (2) What 
was produced ? (3) Is CaC0 3 soluble in water ? (4) How do you 
determine whether or not a gas is C0 2 ? (5) How does the product 
from this experiment compare with that from the burning candle ? 

In the ventilation of dwellings, barns, and stables, it 
is necessary that the products of respiration be removed 
as completely as possible and not allowed to accumulate 
and endanger health. Pure air is as important as pure 
food or water. Impure air is frequently the cause of 
disease, and indirectly it may, by lowering the vitality of 
the individual, prepare the way for disease. When 
gasoline or kerosene is used as fuel, more thorough ventila- 
tion is necessary than when wood or coal is used, because 
the products of combustion from the gasoline and kerosene 
are given off into the room instead of being carried out 
through the chimney. The subject of ventilation, which 
forms a part of sanitary chemistry, is, as a rule, given too 
little attention. 

69. Ammonium Compounds. — When nitrogenous or- 
ganic compounds decay, ammonia gas, NH 3 , is given off. 
Since nitrogenous animal and vegetable matters are con- 



66 



AGRICULTURAL CHEMISTRY 



stantly undergoing decay, some ammonia is always in 
the air. The ammonia gas unites with the carbon dioxid 
and forms ammonium carbonate. In barns and stables 

where the ventilation is poor, 
abnormal amounts of carbon 
dioxid and ammonia are formed 
from the respiration and waste 
products of animals. When 
carbon dioxid forms to such an 
extent that it produces a white 
coating upon stones and boards, 
it shows enough ammonium 
carbonate to be injurious to 
animals. Nitrogen, in traces, 
in the form of ammonium 
nitrate and nitrite, is also 
present in the air. The amount 
of combined nitrogenous com- 
pounds in the air is small and 
not sufficient to furnish food 
for plants. 

70. Moisture. — The amount 
of moisture in the air ranges 
between wide limits, from com- 
plete saturation to desert con- 
ditions. When the air contains all the moisture it can 
hold, it is said to be saturated. In temperate climates, 
the humidity, or per cent of saturation, ranges be- 
tween 60 and 85. The amount of moisture in the air 
has an influence upon plant growth, rather because it 
modifies the conditions of the atmosphere than because 
it furnishes moisture directly to plants. The humidity 
of the air also influences many farm operations, as the 




Fig. 37. — Ventilating flue in chim 
ney for removing foul air. 



AIR 67 

curing of cheese, which is best effected in an atmosphere 
containing about 85 per cent of moisture. 

71. Atmospheric Constituents Present in Small 
Amounts. — Ozone and hydrogen peroxid are oxidizing 
agents, present in the air only in traces. Ozone is a 
modified or allotropic form of oxygen. It is more active 
than ordinary oxygen. Hydrogen peroxid (H2O2) readily 
gives up one of its atoms of oxygen for oxidation purposes. 
H 2 2 = H 2 + O. Argon, krypton, neon, and penon 
are elements which are in the air in small amounts. Argon 
makes up about 1 per cent of the volume of the air, 
and is like nitrogen in many of its chemical character- 
istics, but is even more inactive and inert than nitrogen ; 
it is the most inactive element known. When argon is 
liquified it is not supposed to take any direct part in 
animal or plant life. 

72. Liquid Air. — As both nitrogen and oxygen can 
be liquefied, and air is a mechanical mixture of these ele- 
ments, it necessarily follows that air can be liquefied. 
To accomplish this, air is cooled and then subjected to a 
pressure of 2500 pounds per square inch. Liquid air 
may vary in its nitrogen and oxygen content. It is a 
colorless liquid, and boils at — 19 1°. 

73. Organic Impurities. — Dust, dirt, and impurities 
in the air vary with conditions, as rainfall, local influences, 
and sources of contamination. Fine particles of dust, 
containing decaying vegetable matter, are carried long 
distances by the wind. This decaying vegetable matter 
often contains spores of disease germs. The dust and 
impurities in the air can be observed when a beam of 
sunlight finds its way into a room ; then the particles of 
dust will be seen floating in the air. When the air in 
a room is not in motion, the dust particles separate and 



68 AGRICULTURAL CHEMISTRY 

settle very much as fine clay separates from water which 
is not disturbed. There are many different kinds of 
organic impurities in the air. The most objectionable 
are decayed refuse matters, particularly of animal origin. 
The air which passes over swampy, undrained land is 
often contaminated with impurities. 

74. Air as a Source of Food. — In both animal and 
plant life, air plays an important role. It contains 
oxygen necessary for the existence of animals and carbon 
dioxid essential as food for plants. Over 90 per cent of 
the total food of our agricultural and useful plants is ob- 
tained from the air as carbon dioxid, or from rain which 
finds its way into the soil. Food which is oxidized in 
the body requires oxygen for combustion. Hence it will 
be seen that the air is the source of the larger portion of 
the total food of both plants and animals. 



CHAPTER X 
Acids, Bases, Salts, and Neutralization 

75. Classification of Elements. — Elements are di- 
vided into two classes: (1) acid-forming elements, and 
(2) base-forming elements. This division is made accord- 
ing to the properties of the elements. 

The basic elements are commonly called metals : iron, 
copper, silver, and lead are examples. The basic elements 
form, with H and O, bases or hydroxids, as KOH and 
NaOH. A base is a compound composed of a metal in 
combination with OH, the hydroxyl radical. This radical 
can be replaced by an acid-forming element. 

An acid is a compound containing hydrogen which 
can be replaced by a metal. In the preparation of hydro- 
gen, the H of HC1 is replaced with zinc. The acid- 
forming elements, with hydrogen, and with H and O, 
form acids. 

Bases and acids are opposite in character and proper- 
ties. Acids color blue litmus red, bases color red litmus 
blue. For purposes of study, the different acid- and 
base-forming elements are subdivided into families and 
groups which have definite relationships and common 
characteristics. 

76. Salts. — When an acid and a base are brought to- 
gether, a chemical reaction takes place, known as neutral- 
ization. The product is a salt. A salt is an acid in which 
the hydrogen has been replaced by a metal. It is formed 
by the union of acid- and base-forming elements. Salts are 

69 



70 AGRICULTURAL CHEMISTRY 

neutral compounds. In the study of acids, bases, and 
salts, the character of the compound can always be deter- 
mined from the formula as Ca(OH) 2 . Calcium hydrate 
is a base because it contains the hydroxyl radical OH. 
CaCl2 is a salt because it is composed of the acid-forming 
element CI and the base-forming element Ca. HC1 is 
an acid because it is composed of hydrogen and the 
acid-forming element CI and the H can be replaced by a 
metal. Acids and bases do not exist as such to any ap- 
preciable extent in nature. Salts are neutral compounds 
and the materials most extensively found. In the table, 
Section 15, the characteristic properties of some of the 
elements, as acid- or base-forming, are given. A few 
elements, as will be discussed later, have both acid and 
basic characteristics. 

77. Radicals. — A radical is a group of elements which 
enters into chemical combination like a single element. 
When three elements combine to form a compound the 
combination is made in the following way : Two of the 
elements first form a radical, and then this radical com- 
bines with the third element. Every radical has its own 
valence, which is independent of that of its separate atoms. 
A radical can exist only in chemical combination ; it 
cannot be separated. Its individuality as a radical exists 
only when in combination. The elements which unite 
to form a radical do not do so according to the law of 
valence. Example : When H, S, and O combine, the S and 
O first form a radical, S0 4 , which has a valence of 2. Two 
atoms of H combine with one S0 4 radical and form H 2 S0 4 . 
NH 4 is the ammonium radical, with a value of 1, and 
deports itself as a metal, forming ammonium salts with 
acid radicals as (NH 4 )2S0 4 . There are only a few of the 
more common radicals which require special study at this 



ACIDS, BASES, SALTS, AND NEATRALIZATION 7 1 



stage 


of the work. 


Some of the more common n 


are : 








Radi- 
cal. 


Valence. 


Compounds formed 
with H. 


Compounds formed 
with metals. 


C0 3 


2 


Carbonic acid 


Carbonates 


C10 3 


I 


Chloric acid 


Chlorates 


N0 3 


I 


Nitric acid 


Nitrates 


P0 4 


3 


Phosphoric acid 


Phosphates 


OH 


1 


Water 


Hydroxids 


Si0 3 


2 


Silicic acid 


Silicates 


N0 2 


1 


Nitrous acid 


Nitrites 


S0 3 


2 


Sulfurous acid 


Sulfites 


S0 4 


2 


Sulfuric acid 


Sulfates 



78. Naming of Acids. — Acids are named according to 

the characteristic acid element or radical present, as sul- 
furic acid, H0SO4, in which S is the characteristic acid 
element. The most common acids have the ending ic. 
Some acids have an ous ending, as H 2 S0 3 , sulfurous 
acid. The acid which has the smaller amount of oxygen 
has the ending ous, while the acid with the larger amount 
of oxygen has the ending ic. 

Name the following acids: HN0 3 , HN0 2 , H 2 S0 4 , 
H 2 S0 3 , H3PO4, H3PO3, H 3 As0 4 , H 3 As0 3 . 

79. Naming of Bases. — Bases are named according to 
the characteristic base element which they contain. All 
bases are called hydroxids, as calcium hydroxid, Ca(OH) 2 , 
and potassium hydroxid, KOH. 

The rule in regard to the endings ic and ous applies in 
the case of bases as well as in that of acids ; that is, when 
an element forms two hydroxids, the ending ic is applied 
to the one with the larger amount of hydroxyl, and the 
ending ous to the one with the smaller amount. 

Name the following bases : Mg(OH) 2 , NH 4 OH, NaOH, 
Fe(OH) 2 , Fe(OH) 3 , Al(OH) 3 , CuOH, Cu(OH) 2 . 



72 AGRICULTURAL CHEMISTRY 

80. Naming of Salts. — Salts are named according to 
the acid and base elements which they contain, as K 2 S0 4 , 
potassium sulfate, composed of potassium, K, and the 
sulfate radical, S0 4 . Most salts have an ending ate. 
A few have an ending ite. The salts derived from the 
acids with the ic ending always have the ate ending, as 
sulfuric acid, which produces sulfates, phosphoric acid, 
phosphates, and nitric acid, nitrates. The acids ending 
with ous produce salts which end in ite, as nitrous acid 
produces nitrites, and sulfurous acid, sulfites. Salts 
that are composed of only two elements always have an 
ending of id, as sodium chlorid, NaCl, and sodium sulfid, 
Na 2 S. 

81. Double Salts. — A double salt is one that is com- 
posed of two base elements in combination with one acid 
radical, as NaKS0 4 , sodium potassium sulfate. Double 
salts are formed from acids which contain two replaceable 
hydrogen atoms, as H2SO4, by replacing one of the H 
atoms with one base element and the remaining H atom 
with another base element. This is represented graphi- 
cally as follows : 

Hv Na v 

H 2 S0 4 = >S0 4 = >S0 4 . 

82. Acid Salts. — An acid salt is one in which only a 
part of the H of the acid has been replaced. An acid 
salt always contains H, a metal, and a radical. HNaS0 4 
is acid sodium sulfate, as only one H atom has been 
replaced with Na. A normal salt contains no replace- 
able H. 

83. Basicity of Acids. — Acids with one replaceable H 
atom are called monobasic acids, as HC1 and HNO3. 
Acids with two replaceable H atoms are dibasic, as H 2 S0 4 , 



ACIDS, BASES, SALTS, AND NEUTRALIZATION 



73 



H 2 Si0 3 , and H2CO3. When an acid contains three replace- 
able H atoms, it is tribasic, as H3PO4. 

84. Two Series of Salts. — When a base element has 
more than one valence, it forms two series of salts. For 
example, Fe has a valence 
of 2 and 3. The first series 
of salts is known by the ending 
ous. The second series has an 
ic ending. The one ending 
means that the compound is 
formed from the lower valence 
of the element, as FeCl 2 , ferrous 
chlorid, while FeCl 3 is ferric 
chlorid. There are two series 
of copper salts ; CuCl is called 
cuprous chlorid, and CuCl2, 
cupric chlorid. 

Name the following salts : 
FeCl 2 , FeCl 3 , FeS0 4 , Fe 2 (S0 4 ) 3 , 
Fe(N0 3 ) 2 , Fe(N0 3 ) 3 , Fe(OH) 2 , 
Fe(OH) 3 , HgCl, HgCl 2 , SmCl 2 , 
SnCl 4 , MnCl 4 , MnCl 2 . 

Experiment 10. — Neutralization 
and preparation of salts. Obtain two 
burettes for these experiments. Meas- 
ure out 5 cc. of concentrated HC1 
and 95 cc. of water; after mixing, 
fill one of the burettes with this 
diluted HC1 (Fig. 38). Use your 
funnel for filling the burette, and then 
carefully wash the funnel. Prepare 
a dilute solution of NH 4 OH, using 90 cc. of water and 10 cc. of the 
shelf NH4OH. After mixing, fill the second burette with this prepa- 
ration of diluted NH 4 OH. Before using the solution in the burette, 




Fig. 38. — Burette. 



74 AGRICULTURAL CHEMISTRY 

it should be lowered to the zero point by carefully opening the 
pinchcock. Always allow the tip of the burette to be filled with 
the solution before beginning the experiment. 

Into a small beaker, measure from the burette exactly 20 cc. 
NH4OH, with 10 or 12 drops of cochineal solution, which is changed 
to a deep purplish color by the alkali ; then slowly add HC1 from 
the other burette, constantly stirring the solution in the beaker 
until a decided change in color is observed. When all of the NH 4 OH 
has been neutralized, the solution has a yellowish red color. Note 
the number of cubic centimeters of HC1 used for neutralizing the 
20 cc. of NH4OH solution. Add a drop or two from the NH 4 OH 
burette and note if there is a change of color. When the solution 
is neutralized, one or two drops of HC1 or NH 4 OH should give a 
decided change of color. If too much acid has been used, add a 
measured amount from the NH 4 OH burette until the solution is 
neutralized. Finally note the total quantity of HC1 and NH 4 OH 
used. Repeat this experiment, using 20 cc. of the HC1 solution. 

Questions. — (1) What was formed When the HC1 neutralized the 
NH4OH solution ? (2) Write the reaction. (3) What would be 
the result if the neutralized solutions were evaporated to dryness ? 
(4) Calculate the amount of HC1 required to neutralize 1 cc. of 
NH4OH. 

Experiment 11. — Neutralization. Repeat Experiment 10, using 
dilute H2SO4 and NaOH solutions that have been prepared for this 
experiment. After completing the experiment, clean the . burettes 
thoroughly. 

Questions. — (1) What was formed when H 2 S0 4 neutralized 
NaOH ? (2) Write the chemical reaction. (3) What was formed 
as the products of this reaction ? (4) How can the salt product be 
obtained ? (5) In writing the reaction, why do we use 2 NaOH in- 
stead of NaOH ? (6) How does the product of Experiment 10 
differ from the product of Experiment 11 ? (7) What other acids 
could be used for neutralizing NaOH and NH 4 OH ? (8) What 
other bases could be used for neutralizing HC1 and H 2 S0 4 ? (9) What 
is an acid ? (10) What is a base ? (11) What is a salt ? (12) Which 
do we find most abundantly in nature, acids, bases, or salts ? Why ? 

Experiment 12. — Preparation of a salt. Put 10 cc. dilute HC1 
and 10 cc. water into an evaporator. Measure out 10 cc. of NaOH 
into a beaker and add 50 cc. water. Add this diluted NaOH to the 



ACIDS, BASES, SALTS, AND NEUTRALIZATION 



75 




Fig. 39. — Sodium 
chlorid crystals (com- 
mon salt). 



evaporator a little at a time until the solution is neutral to litmus 
paper. Do not dip the paper into the solution, but transfer a drop 
by means of a glass rod from the evaporator to the paper. In case 
too much NaOH has been used, add a drop 
or two of the acid. Bases or alkalies turn 
red litmus paper blue, while acids turn blue 
litmus paper red. When the solution is neutral, 
it has no perceptible action upon litmus paper. 
Place the evaporating dish upon the sand bath, 
and apply heat until the solution is evapor- 
ated to dryness. Carefully regulate the flame 
so as to avoid excessive heating. This will 
prevent spattering when the solution becomes concentrated. 

Questions. — (1) What is left in the evaporator ? (2) From what 
was it produced ? (3) Write the chemical reaction. (4) Taste 
some of the material in the evaporating dish. How is it possible for 
this material to be formed from two such unlike compounds as HC1 
and NaOH ? (5) What is neutralization ? (6) Are definite amounts 
by weight of HC1 and NaOH required for neutralization ? (7) How 
many molecules of HC1 are required to neutralize one of NaOH ? 
(8) How much does a molecule of HC1 weigh ? (9) Of NaOH ? 
(10) How many parts by weight of each must be taken for neutrali- 
zation ? (n) How does this illustrate the law of definite proportion ? 



CHAPTER XI 
Hydroclhloric Acid, Chlorin, and Chlorids 

85. Occurrence. — The element chlorin is never found 
in a free state in nature, but is always in combination 
with other elements, as with sodium, forming sodium 
chlorid. With hydrogen, chlorin forms hydrochloric 
acid. 

86. Preparation. — Hydrochloric acid is produced by 
the action of H 2 SO on NaCl, the reaction being 2 NaCl + 
H2SO4 = Na 2 S0 4 + 2 HC1. Heat is applied, and the 
hydrochloric acid gas is expelled and collected in water. 
In the preparation of hydrochloric acid, .the CI part of 
the compound is supplied by the NaCl, while the sulfuric 
acid furnishes the hydrogen. Hydrochloric acid can 
also be made by direct union of the elements hydrogen 
and chlorin. It is prepared in the laboratory in the 
following way : 

Experiment 13. — Preparation of hydrochloric acid. Arrange 
the apparatus as shown in Fig. 40. A sand bath, containing sand, 
is placed upon either the tripod or the large ring of the iron ring 
stand. Tube B connects flask A with Woulff bottle C, which con- 
tains 100 cc. of water. The tube is made from a piece of glass 
tubing 22 to 24 inches long, with one right-angled bend about 3 
inches from the end, and another, parallel and about 6 inches from 
the first bend. This tube is connected with both flask A and the 
Woulff bottle by means of tight-fitting corks. Tube B passes into 
the bottle, but not below the surface of the liquid. Through a tight- 
fitting cork in the middle neck of Woulff bottle C passes a safety 
tube so adjusted that it dips just below the surface of the water in 

76 



HYDROCHLORIC ACID, CHLORIN, AND CHLORIDS 



77 



C. This safety tube is a straight piece of glass tubing, 9 or 10 
inches long. Woulff bottle C is connected with a second Woulff 
bottle by means of a bent tube which passes below the water in the 
second bottle, but is 
above the water in the 
first bottle. The ap- 
paratus, as constructed, 
allows the gas which is 
generated in flask A to 
pass through into C and 
saturate the water. 
Some of the acid passes 
over into the second 
Woulff bottle. Since the 
delivery tubes in C do 
not pass below the sur- 
face of the liquid, and 
the pressure is equalized, 
no liquid can be drawn 
back into flask A. 

Place 15 grams so- 
dium chlorid (NaCl, 
common salt) and 30 cc. 
concentrated H 2 S0 4 in 
flask A. Apply heat to 
the flask, and after ten 
minutes remove the 
burner and test the liquid in both Woulff bottles with litmus paper. 
Then make the following tests : 

(1) Disconnect the delivery tube and test the escaping gas with 
wet litmus paper. (2) Collect a little of the gas in a test tube, and 
test it with a burning splinter. (3) Put 2 or 3 cc. of silver nitrate 
(AgN0 3 ) into a test tube and then a like amount of HC1 from the 
first Woulff bottle. Observe the result. (4) Leave the test tube 
and contents exposed to strong sunlight for a few minutes. (5) Put 
a small piece of zinc into a test tube and cover it with some of the 
acid from the first Woulff bottle. Observe the result. 

Questions. — (1) What chemical reaction took place when H2SO4 
and NaCl were brought together? (2) Is HC1 a solid, liquid, or 




Fig. 40. — Preparation of hydrochloric acid. 



78 AGRICULTURAL CHEMISTRY 

gas? Why? (3) Color? (4) Is it soluble in water? Why? 
(5) What was formed when the HC1 was added to the test tube con- 
taining AgN0 3 ? Give the reaction. (6) Is HC1 combustible or a 
supporter of combustion ? (7) What is a chlorid ? (8) What effect 
would HC1 gas have upon plants ? 

87. Properties. — Hydrochloric acid is a colorless gas, 
soluble in water. When exposed to the air, it combines 
with the moisture. The concentrated acid used in the 
laboratory is a solution of about 40 per cent HC1. Chem- 
ically, HC1 is an active acid, and is neither combustible 
nor a supporter of combustion. When it neutralizes 
bases, chlorids are always formed. Hydrochloric acid 
is distinguished from other acids by its reaction with 
silver nitrate, a white precipitate of silver chlorid being 
produced which is soluble in ammonia and is blackened 
in the sunlight. Hydrochloric acid is used extensively 
in the laboratory in the preparation of various compounds, 
and for the production of chlorin. 

88. Preparation of Chlorin. — Chlorin is made by 
the action of an oxidizing agent, as manganese dioxid, 
upon hydrochloric acid, manganese chlorid, water, and 
chlorin gas being formed as products. The reaction is 
Mn0 2 + 4 HC1 = MnCl 2 + 2 H 2 + 2 CI. In this reac- 
tion the valence of manganese is changed from 4 to 2, 
and as a result free chlorin gas is liberated. The method of 
preparation in the laboratory is as follows : 

Experiment 14. — Preparation of chlorin. It is preferable to set 
up the apparatus for generating chlorin under one of the hoods. 
Arrange the apparatus as shown in Fig. 41. Place 10 grams of 
Mn0 2 and 15 or 20 cc. of HO in flask A. By means of delivery 
tube B, and a tight-fitting cork, the CI gas, when generated, passes 
into the large cylinder, in which has been placed a green leaf, a 
piece of colored cloth, and paper upon which is some writing. The 



HYDROCHLORIC ACID, CHLORIN, AND CHLORIDS 



79 



Give the physi- 
Cl gas, odor, 
(2) What caused 



delivery tube passes through the hole in the ground-glass plate, 

without any cork. To generate the chlorin, apply gentle heat to 

the flask, and as soon as the cylinder is nearly filled with the CI 

gas, which can be observed by its 

color, remove the flame so as to 

prevent any of the gas from escaping 

into the room. Do not inhale any 

of the fumes, as they are irritating 

to the throat and lungs. Make 

the following tests : 

(1) Observe the effect which the 
chlorin gas has upon the cloth, 
paper, and leaf. (2) To the cylin- 
der, add 5 cc. water containing two 
or three drops of indigo solution. 
Observe the result. 

Questions. — (1) 
cal properties of 
weight, and color. 

liberation of the CI gas from the 
HC1? (3) Write the reaction. 
(4) What are some of the chemical 
properties of chlorin as observed 
from the changes which have taken 
place in the materials in the cylin- 
der? (5) What is a chlorid ? 
(6) Name five compounds contain- 
ing chlorin. (7) Why is CI gas employed as a disinfectant ? Ex- 
plain its action as a disinfectant. (8) What is bleaching powder, 
and how is it used as a disinfectant ? (9) NaCl is necessary for 
animal life ; CI is one of its elements and CI is destructive to animal 
life ; why can you not conclude that NaCl containing CI is de- 
structive to animal life ? 

89. Properties. — Physically considered, chlorin is a 
heavy, greenish yellow gas, with a penetrating, suffo- 
cating odor. Chlorin gas is poisonous. Chemically, it 
is an active element and has strong affinity for nearly all 
other elements. It readily combines with metals, form- 




Fig. 41. — Preparation of chlorin. 



80 AGRICULTURAL CHEMISTRY 

ing chlorids, and light and heat are evolved during the 
reaction. Chlorin is an active bleaching reagent, as it 
changes the composition of vegetable dyes, thus destroy- 
ing their color. Bleaching powder is a mixture of cal- 
cium hypochlorite and calcium chlorid, and when used, 
chlorin is liberated. Chlorin is also a disinfectant and a 
germicide, for it is destructive to life, particularly to the 
lower forms. It is used extensively for both bleaching 
and disinfecting purposes. Chlorin takes no part directly 
in life processes, although its compounds, particularly 
sodium chlorid, are necessary as mineral food for animals. 

90. The Chlorin Group of Elements. — Fluorin, 
chlorin, bromin, and iodin constitute a natural group of 
elements, known as the chlorin family. These elements 
are all closely related. They form similar acids with 
H, and similar salts with the metals. Some of the most 
important relationships and points of difference between 
members of the chlorin family will be observed in the 
following table : 

Physical 
Element. At. wt. conditions. H compound. Na compound. 

Fluorin 19 Light gas HF1 NaFl 

Chlorin 35-45 Heavy gas HC1 NaCl 

Bromin 79-95 Liquid HBr NaBr 

Iodin 126.85 Solid HI Nal 

91. Chlorids. — Combined with the metals, chlorin 
forms chlorids. As a class, the chlorids are quite stable 
compounds, inasmuch as chlorin has strong affinity for 
nearly all of the metals. The properties of the different 
chlorids vary with the metal with which the chlorin is 
combined. The chlorids do not take such a direct part 
in plant as in animal nutrition. When present in either 
soil or water in any appreciable amount, the soil is sterile 



HYDROCHLORIC ACID, CHLORIN, AND CHLORIDS 8l 

and the water is not suitable for either drinking or irri- 
gation purposes. Sodium chlorid is found in nature most 
abundantly of any of the chlorids. 

Problem i. — How much H 2 S0 4 is required to combine with 2000 
pounds NaCl in making HC1 ? 

Problem 2. — How much HC1 can be made from 2000 pounds of 
NaCl? 

Problem 3. — How much Na 2 S0 4 is produced when 2000 pounds 
NaCl are used for making HC1 ? 



CHAPTER XII 
Nitric Acid and Nitrogen Compounds 

92. Occurrence. — Nitric acid does not occur in nature 
in a free state, but as nitrates or salts of nitric acid. 
Since all normal nitrates are soluble in water, they are 
never present in great abundance in soils. In regions 
of scant rainfall, where climatic conditions have been 
favorable for the formation of nitrates, deposits of nitrate 
of soda are occasionally found. The nitrifying organisms 
of the soil, when supplied with food, moisture, suitable 
temperature, and other requisite conditions, produce 
nitrates which are utilized as food by plants. The process 
of nitrification which takes place in the soil results in 
changing the inert and unavailable nitrogen to a soluble 
and available condition. 

93. Preparation. — The same principle is applied in the 
preparation of nitric acid as in the preparation of hydro- 
chloric acid. Nitric acid is produced by the action of 
H2SO4 upon a salt ; when a chlorid is used, hydrochloric 
acid results, and when a nitrate is used, nitric acid is the 
product. The reaction with sodium nitrate is : 2 NaN03 
+ H 2 S0 4 = Na*S0 4 + 2 HNO3. 

Experiment 15. — Preparation of nitric acid. Special care should 
be exercised by the student in the preparation of nitric acid, be- 
cause if any is spilled on the hands, it causes painful burns and 
wounds that are difficult to heal. Provided the student is careful 
and follows the directions given, there is no danger. Arrange the 
apparatus as shown in Fig. 42. The delivery tube used in the 
preparation of NH 3 may be used for this experiment. A cork stopper 
should be used. If necessary, a brick or block may be placed under 

82 



NITRIC ACID AND NITROGEN COMPOUNDS 



83 



the cylinder. The delivery tube should pass into and nearly to the 
bottom of a test tube which is immersed in cold water in the cylin- 
der. Put 15 cc. concentrated sulfuric 
acid (H2SO4) and 10 grams of either 
sodium nitrate (NaN0 3 ) or potassium 
nitrate (KN0 3 ) into the flask and apply 
heat until about 4 or 5 cc. of HN0 3 are 
distilled and collected in the test tube. 
Do not remove the flame unless the end 
of the delivery tube is above the liquid 
in the test tube, otherwise the liquid will 
be drawn back into the flask. 

Make the following tests with HN0 3 . 
(1) Remove a drop of the acid by means 
of a glass tube, and apply it to a piece 
of either woolen cloth or silk. Observe 
the result. (2) Place a few drops of 
indigo solution in a test tube containing 
5 cc. of water, then add about 2 cc. of 
HNO3. Observe the result. (3) Place a 
small piece of copper in the test tube 
containing the remainder of the acid. 
Observe the result. If no reaction takes 
place, add a little water. Do not pour 
the contents of the flask into the sink or 
waste jars until cool, otherwise the hot acid 
coming in contact with cold water may cause spattering of the acid. 

Questions. — (1) Why was H 2 S0 4 used in the preparation of this 
compound ? (2) What material supplied the N0 3 radical ? (3) Write 
the reaction which took place in the flask after heat was applied. 
(4) Is HNO3 a solid, liquid, or gas ? What is the proof ? (5) What 
caused the red fumes to be given off when the copper was added to 
the test tube ? (6) Does HN0 3 give off H when a metal is added to 
it ? Why ? (7) Why did the HN0 3 bleach the indigo solution ? 
(8) Why is ordinary HN0 3 colored yellow ? (9) Is HN0 3 an active 
or inert chemical ? (10) What is a nitrate ? 




a* 



Fig. 



42. — Preparation of 
nitric add. 



94. Properties. — When pure, nitric acid is a colorless 
liquid; the commercial acid has a yellow color because 



84 AGRICULTURAL CHEMISTRY 

of the presence of oxids of nitrogen. Nitric acid is an 
active oxidizing reagent, and when metais, as copper and 
iron, are dissolved in it, brown fumes of NO2 are given 
off because the hydrogen, as soon as liberated, is oxidized 
by the excess of acid, and N0 2 is formed. H + HN0 3 = 
H 2 + NO2. Nitric acid imparts a permanent yellow 
color to wool, silk, and all albuminous matter. 

95. Importance. — In the laboratory nitric acid is used 
as an oxidizing agent. Commercially it is employed in 
the dyeing of cloth, although it has a tendency to weaken 
the wool fibers. Salts of nitric acid are important because 
they are of much value as plant food, and particularly 
in the manufacture of commercial fertilizer, where they 
supply nitrogen. Potassium nitrate is used in the manu- 
facture of gunpowder. Nitrates are of great importance 
in agriculture. 

Ammonia 

96. Occurrence. — Ammonium compounds are present 
in small amounts in the air, in rain water, and in the soil, 
and are produced from decaying nitrogenous organic 
matter. The chief source of the ammonia which serves 
as the basis for the preparation of ammonium salts is 
the ammonia water obtained in the process of purifying 
illuminating gas made from soft coal. The nitrogen 
compounds of the coal form ammonia gas, NH 3 , during 
the destructive distillation process. 

97. Preparation. — In the laboratory, ammonia is 
usually prepared from ammonium chlorid by treatment 
with a strong base, as Ca(OH) 2 . The reaction is : 

2 NH4CI + Ca(OH) 2 = CaCl 2 + 2 NH 4 OH. 

Experiment 16. — Preparation of ammonia. Arrange apparatus 
as directed for the preparation of HC1 (see Fig. 40). Into flask A, 



AMMONIA 85 

place 10 grams each of dry ammonium chlorid, NH 4 C1, and powdered 
calcium hydroxid, Ca(OH) 2 , and 25 cc. water. Barium hydroxid, 
Ba(OH) 2 , may be used in place of the Ca(OH) 2 . When properly con- 
nected, apply heat to the sand bath from eight to twelve minutes. 

Tests for Ammonia. — (1) Test the gas with wet litmus paper. 
Note the result. (2) Test the water in both Woulff bottles with 
litmus paper, and note the result. (3) In an evaporator place 5 cc. 
HC1 and 10 cc. water. Disconnect the delivery tube from Woulff 
bottle C, and pass some of the fumes of the escaping gas over the 
acid in the evaporator. Avoid inhaling any of the gas. (4) Collect 
some of the gas in a test tube and then place the test tube inverted 
in a cylinder about one third full of water. (5) Add 5 cc. of the 
NH 3 solution from either of the Woulff bottles to 5 cc. of a solution 
of alum. Note the result. 

Questions. — (1) What material supplied the NH 4 part of the 
NH4OH ? (2) What caused the gas to be liberated from these ma- 
terials ? (3) What chemical reaction took place in flask A after 
the heat was applied ? (4) Why was water used in the Woulff 
bottle ? (5) What did the water and the N 3 H gas form ? (6) What 
reaction did the NH 3 gas and the N 4 HOH give with the litmus 
paper? (7) Why was not this gas given off into the room ? (8) Why 
was not N3H collected over water, like H, N, and ? (9) What 
caused the water to rise in the test tube ? (10) Why have you reason 
to believe that the N 4 HOH caused a chemical reaction when added 
to the solution of alum ? 

98. Properties and Uses. — Ammonia is a colorless, 
non-combustible, pungent gas, which unites with water 
to form ammonium hydroxid, NH 4 OH, a basic compound. 
It is completely soluble in water, from which it is easily 
liberated by heat. The gas can be reduced to liquid 
form by cold and pressure. Liquefied ammonia reverts 
to a gas upon removal of the pressure, and in so doing, 
heat is absorbed from surrounding bodies. If this heat 
is absorbed from water, the temperature of the water 
is lowered sufficiently to produce ice. This property of 
liquefied ammonia is taken advantage of for the artificial 



86 AGRICULTURAL CHEMISTRY 

production of ice, and for refrigerating purposes. The 
transportation of perishable food materials is rendered 
possible by this method of refrigeration. 

In the laboratory, ammonium hydroxid is used exten- 
sively as a reagent for neutralizing acid solutions and 
precipitating insoluble hydroxids. Ammonium salts, ex- 
cept in very small amounts, are destructive to plants, 
(NH 4 ) 2 S0 4 is less injurious than either NH 4 C1 or (NH 4 ) 2 C0 3 , 
and may be used as a fertilizer. 

Dilute solutions of the ammonium compounds serve 
as food for plants, supplying them with nitrogen, which 
is used for producing, within the plant cells, complex 
nitrogenous compounds, as proteids. Ammonium com- 
pounds supply only one form of nitrogenous plant food. 
Because of its being a volatile alkali, ammonia is valuable 
as a reagent for softening water. 

99. Oxids of Nitrogen. — Nitrogen forms five com- 
pounds with oxygen : 

N2O nitrogen monoxid or nitrous oxid. 

N2O2 nitrogen dioxid or nitric oxid. 

N2O3 nitrogen trioxid or nitrous anhydrid. 

N2O4 nitrogen tetroxid. 

N2O5 nitrogen pentoxid or nitric anhydrid. 

While the oxids of nitrogen do not serve either as plant 
or animal food, they are nevertheless important, and a 
study of them is necessary in order to understand the 
subject of nitrogen. 

100. Anhydrids. — An anhydrid is an oxid of an acid 
element, or the product which is left after the elements 
which form water are abstracted from an acid. SO3 is 
sulfuric anhydrid, and is formed by abstracting H 2 
from H 2 S0 4 . H 2 S0 4 = H 2 + S0 3 . N 2 5 is nitric anhy- 
drid, derived from two molecules of HNO3. 2 HNO3 = 
H 2 + N2O5. 



AMMONIA 87 

Derive and name the anhydrids of the following acids : 
2 H3PO4, H2CO3, H 2 Si0 3 , 2 HN0 2 , H 2 S0 3 . 

101. Law of Multiple Proportion. — When nitrogen 
and oxygen combine, the number of parts of nitrogen in 
the various compounds is constant ; namely, 28 parts 
by weight in each compound. The number of parts of O 
is always a multiple of the first combination, N 2 ; that 
is, it is either 2, 3, 4, or 5 times as much in the other 
compounds as in the first. This is an example of the 
law of multiple proportion where two elements combine 
in more than one way. It is to be noted that the amount 
by weight of one of the elements remains constant in all 
the combinations, while the amount of the other element is 
always a multiple of the first combination. 

The law of definite proportion holds true for each in- 
dividual compound, while the law of multiple proportion 
applies to the entire series, and is a broader application 
of the law of definite proportion. 

102. Utilization of Atmospheric Nitrogen. — When a 
current of nitrogen obtained from the air is passed through 
a mixture of lime and coal heated in an electric furnace, 
a chemical union of calcium, carbon, and nitrogen is 
effected, calcium cyanamid, CaCN 2 , being formed. This 
compound is used as a fertilizer, and supplies the element 
nitrogen to plants. By this process of manufacturing 
CaCN 2 , the inactive nitrogen of the air, is combined and 
made available for the production of crops. 

103. Importance of the Nitrogen Compounds. — The 
compounds of nitrogen, particularly nitrates and ammo- 
nium compounds, are of importance in agriculture as they 
serve as food for plants. They are difficult to retain in 
soils because of their solubility and the volatility of 
ammonia. In human and animal foods, the nitrogenous 



88 AGRICULTURAL CHEMISTRY 

compounds are of importance in many ways and hence, in 
economic agriculture, they receive special consideration. 

Problem i, — How many pounds of HN0 3 can be produced from 
ioo pounds NaN0 3 ? 

Problem 2. — How much H2SO4 is required when 100 pounds 
HNO3 are made ? 

Problem j. — How much NH 4 OH can be produced from 10 pounds 
of NH4CI ? 

Problem 4. — What per cent of NH 4 OH is NH 3 ? 



CHAPTER .XIII 
Phosphorus and its Compounds 

104. Occurrence. — Phosphorus is found in nature in 
combination with oxygen and other elements, forming 
phosphates, as Ca 3 (P0 4 )2- It is never found in a free or 
uncombined state. There is little in soils, but in many 
rocks and minerals, as apatite or phosphate rock, it is 
present in large amounts. It is also in the ash of plants, 
and in animal bodies, particularly as a constituent of 
bones. 

105. Preparation. — It is prepared from bones, which 
are first freed from organic matter by burning. The 
bone ash is treated with sulfuric acid, producing acid 
phosphates, which, when roasted with charcoal, liberate 
free phosphorus. 

106. Properties. — There are two forms of phosphorus : 
the yellow and the red. Yellow phosphorus is a solid 
which ignites at a low temperature. Red phosphorus is 
an allotropic form of the element produced by heating the 
yellow variety in a sealed tube. Yellow phosphorus 
more readily combines with oxygen than does the red, 
and is kept under water to prevent contact with air. 

107. Oxids of Phosphorus. — When phosphorus is 
burned in a current of oxygen or dry air, phosphorus 
pentoxid, P2O5, is obtained. This material is a white 
flocculent mass which readily dissolves in water, forming 
metaphosphoric acid. When phosphorus is burned in a 
limited amount of air, it yields phosphorus trioxid, P 2 3 , 

89 



90 AGRICULTURAL CHEMISTRY 

which after long standing dissolves in water, forming 
phosphorous acid. In fertilizer, soil, and food analysis, 
the amount of phosphorus is expressed in terms of P2O5. 

108. Phosphoric Acid and Phosphates. — Ordinary 
phosphoric acid is produced by the action of H 2 S0 4 upon 
bone ash. 

3 H 2 S0 4 + Ca 3 (P0 4 ) 2 = 2 H3PO4 + 3 CaS0 4 . 

Salts of ortho or ordinary phosphoric acid are the most 
common forms of the acid derivatives. Since this acid 
contains three replaceable H atoms, three salts are formed, 
as : Na 3 P0 4 , normal sodium phosphate ; Na 2 HP0 4 , 
disodium phosphate ; ' and NaH 2 P0 4 , monosodium phos- 
phate. The three calcium salts of phosphoric acid are : 

CaH 4 (P0 4 ) 2 , monocalcium phosphate. 

Ca 2 H 2 (P0 4 ) 2 , dicalcium phosphate. 

Cas(P0 4 ) 2 , tricalcium phosphate. 

In addition to the ordinary phosphoric acid, there are 
other derivatives, as : 

H 3 P0 4 = H 2 -f HPO3 (metaphosphoric acid). 

2 H 3 P0 4 = H 2 + H 4 P 2 7 (pyrophosphoric acid). 

109. Phosphate Fertilizers. — In deposits of phosphate 
rock, the phosphoric acid is mainly in combination with 
calcium as Ca 3 (P0 4 ) 2 , and is of little value as plant 
food until it is treated with H 2 S0 4 and converted into 
monocalcium phosphate, which is soluble and available 
as plant food. Ca 3 (P0 4 ) 2 + 2 H 2 S0 4 = CaH 4 (P0 4 ) 2 + 
2 CaS0 4 . Large amounts of phosphates undergo this 
treatment in the manufacture of commercial fertilizers. 

Experiment 17. — In a beaker on a sand bath, dissolve § gram 
of bone ash in 10 cc. dil. HN0 3 + 20 cc. H 2 ; filter, and to the 
filtrate, while still warm, add 5 cc. ammonium molybdate, and then 
stir. Observe the precipitate, which is a compound of phosphoric 
acid, ammonium, and molybdenum. 



PHOSPHORUS AND ITS COMPOUNDS 91 

Questions. — (1) What was the solvent of the phosphoric acid ? 
(2) Why was the solution boiled and filtered ? (3) Describe the 
color and properties of the precipitate. 

Experiment 18. — Dissolve \ gram of sodium phosphate in 10 cc. 
distilled water, then add 10 cc. of a solution containing \ gram 
CaCl 2 . Observe the result. Write the reaction. Repeat this ex- 
periment, using AICI3 or alum in place of CaCl 2 . 

1 10. Compounds of Phosphorus. — Phosphorus forms 
a large number of compounds, as phosphates, metaphos- 
phates, and pyrophosphates. It also combines with H, 
CI, and I. With H it forms PH 3 , phosphine. Phosphorus 
also enters into combination with C, H, N, O, and S, 
forming complex organic compounds, as nucleo proteids 
and lecithin. It is an element which has a wide range of 
combinations. 

in. Importance of Phosphorus and its Compounds. — 
The compounds of phosphorus, particularly the phos- 
phates, are important in plant development, being forms 
of mineral food essential for crop growth. Agriculturally 
considered, phosphorus is one of the most important of 
the elements. It is stored in the seeds of grains ; and in 
combination with the elements which form the organic 
compounds of plants, it takes an important part in animal 
nutrition. Compounds of phosphorus are used in the 
manufacture of matches, and as poison for insects. Phos- 
phorus forms a large number of compounds, both with 
the metals and with the elements which enter into the 
organic compounds of plant and animal bodies. 

Problem 1. — How much P2O5 in a ton of bones, 80 per cent 
Ca 3 (P0 4 ) 2 ? 

Problem 2. — How much would the P 2 5 in a ton of Ca 2 H 2 (P04)2 
be worth at 5 cents per pound for the P 2 5 ? 

Ca 2 H 2 (P0 4 ) 2 = P 2 5 + 2 CaO + H 2 0. 



CHAPTER XIV 
Sulfur and its Compounds 

112. Occurrence. — Sulfur is found free, and in com- 
bination with other elements ; sulfids and sulfates are the 
compounds which occur most abundantly. Sulfur is 
also found in small amounts in combination with carbon, 
hydrogen, oxygen, and nitrogen, forming the organic 
compounds of plant and animal bodies. 

113. Preparation. — When taken from the mines, sulfur 
is mixed with impurities, as sand and clay, which are 

partially removed by heat- 
ing the sulfur, out of con- 
tact with air, much in the 
same way that charcoal is 
produced. Crude sulfur 

Fig. 43. — Crystals of sulfur. . « i , 

is refined by vaporizing 
and condensing the volatile sulfur upon the surfaces of 
brick chambers, the product being known as flowers of 
sulfur. By drawing off the molten sulfur into wooden 
molds, roll sulfur, or brimstone, is made. 

114. Properties. — Like carbon and a few other ele- 
ments, sulfur has a number of allotropic forms. It may 
assume either an amorphous or several crystalline forms. 
It melts at a low temperature, and when molten sulfur is 
poured into water, a rubber-like, amorphous mass is 
obtained. Sulfur combines with oxygen ; and with the 
metals it forms sulfids. 

92 




SULFUR AND ITS COMPOUNDS 93 

115. Uses. — Sulfur is used in the preparation of sulfuric 
acid, in the production of vulcanized rubber, in the 
manufacture of matches and gunpowder, and for bleach- 
ing and disinfecting purposes. A small amount in the 
form of sulfates is necessary as plant food. 

Experiment ig. — Properties of sulfur. Place 15 grams of sulfur 
in a test tube and heat slowly until it is a thin, amber- colored 
liquid. As the heat increases, notice that it becomes darker until 
black, and so thick and viscid that it cannot be poured from the 
test tube. Continue to apply heat until slightly lighter in color 
and again a liquid. Then pour the sulfur into an evaporating dish 
containing water, and, when cold, examine it and describe its proper- 
ties. Examine the sulfur product or crystals left in the test tube, 
and compare with the original sulfur, using a lens for the purpose. 

Questions. — (1) Are the crystals of sulfur formed by fusion like 
those of the original powdered form ? (2) How is it possible for 
sulfur to assume different physical forms ? (3) Is sulfur soluble in 
water ? (4) What is a sulfate ? Give the formula for one. (5) What 
is a sulfite ? Give the formula for one. (6) What is a sulfid ? 

116. Sulfur Dioxid. — When sulfur is burned either in 
air or oxygen, SO2, a colorless, suffocating, non-combus- 
tible gas is produced. S0 2 combines with water, forming 
H2SO3, sulfurous acid. Sulfur dioxid is used in bleach- 
ing and for disinfecting purposes, as it is alike destruc- 
tive to organic coloring matter and to germ life. 

Experiment 20. — Sulfur dioxid. Fill the deflagration spoon half 
full of sulfur ; ignite, and then lower into a small cylinder contain- 
ing a piece of wet colored cloth and a piece of wet blue litmus paper. 
As soon as the sulfur ceases to burn, remove the spoon and cover 
the cylinder with a glass plate. 

Questions. — (1) What reaction does the S0 2 give with the litmus 
paper? (2) What effect did it have upon the cloth? (3) What 
does the S0 2 form with H 2 ? (4) Is S0 2 a heavy or a light gas ? 
(5) Is it a chemically active substance ? (6) Why does it act as a 
bleaching agent ? (7) Why is it valuable as a disinfectant ? 



94 AGRICULTURAL CHEMISTRY 

117. Sulfuric Acid. — Sulfuric acid cannot be produced 
from sulfates, as HC1 and HN0 3 are from their salts, 
because there is no acid or other material that can be 
used economically for the purpose. H 2 SO is made 
from its elements by the use of an oxidizing agent. The 
different steps in its production are : 

(1) Burning of sulfur, or roasting of some ore, as 
pyrites, which contains sulfur. The S forms with O, S0 2 . 

(2) Union of S0 2 and H 2 0, forming sulfurous acid, 
H 2 S0 3 . 

(3) Oxidation of H 2 S03 to form H 2 S0 4 . This is accom- 
plished by the use of N0 2 reduced to NO, which in turn 
is capable of uniting with the oxygen of the air, re-forming 
N0 2 . NO is used as a carrier of O ; hence the oxygen of 
the air is used indirectly for the oxidation of H 2 S0 3 . The 
different reactions take place simultaneously in lead-lined 
chambers : 

S0 2 + H 2 + N0 2 = H 2 S0 4 + NO. 
NO + O = N0 2 . 

Other and more complicated reactions also take place. 
The crude acid is then concentrated and purified. 

Sulfuric acid is extensively used in industrial opera- 
tions. There is scarcely a chemical product in the prepa- 
ration of which H 2 S0 4 is not used either directly or in- 
directly. H 2 S0 4 takes an important part in the manufac- 
ture of soda, which, in turn, is used for making glass, 
also in the preparation of commercial fertilizers, and of 
many food products. The amount of sulfuric acid which a 
country consumes is a fair index of the extent of its man- 
ufacturing industries. 

118. Properties of H 2 S0 4 . — When pure, it is a colorless, 
heavy, oily liquid. It has a strong affinity for water, 



SULFUR AND ITS COMPOUNDS 95 

with which it combines with evolution of heat. It will 
decompose organic materials containing C, H, and O, 
liberating the H 2 as water, with which it combines, 
while the carbon, which is partially oxidized, separates 
and blackens the acid. When sugar is acted upon by 
concentrated sulfuric acid, this change takes place. 
H2SO4 is used in the laboratory for drying gases, for 
drying the air in desiccators, and for oxidizing purposes, 
as in the determination of organic nitrogen in food mate- 
rials. It is one of the most useful and most extensively 
used of any of the reagents in the laboratory. 

Experiment 21. — Make the following tests with some of the sul- 
furic acid from the reagent bottles : (1) Put 2 or 3 cc. concentrated 
H2SO4 into a test tube ; thrust a splinter of wood into it and leave 
it there for a few minutes. Then remove the splinter from the test 
tube. Wash off the acid and examine the splinter. (2) Place in an 
evaporating dish 5 cc. water and 15 cc. H 2 S0 4 . Stir it with a small 
test tube containing 1 or 2 cc. NH 4 OH. Observe that the heat 
generated by the action of the H 2 S0 4 and water volatilizes some of 
the NH 3 . (3) Put 10 cc. of water and 1 cc. dilute H 2 S0 4 into a test 
tube. Then add 2 or 3 cc. of barium chlorid, BaCl 2 . Observe the 
result. 

Questions. — (1) Why is not H 2 S0 4 made from sulfates ? (2) Why- 
is heat produced when water and H 2 S0 4 are mixed ? (3) What 
use was made of this heat in test No. 2 ? (4) What caused the 
precipitate when BaCl 2 was added ? (5) Write the reaction. 
(6) What is the name of the product ? (7) What are some of the 
uses of H 2 S0 4 ? (8) How many kinds of salts does H 2 S0 4 form ? 
(9) Why is nitric oxid used in the manufacture of H 2 S0 4 ? (10) What 
are the physical properties of H 2 S0 4 ? (11) Of what agricultural 
value is H 2 S0 4 ? (12) Does H 2 S0 4 dissolve lead? (13) Why does 
commercial H 2 S0 4 often appear dark-colored or deposit a fine, white 
sediment ? 

119. Sulfates. — Sulfuric acid is a dibasic acid, and 
hence may form two series of salts, as NaHS0 4 , primary 



9 6 



AGRICULTURAL CHEMISTRY 



sodium sulfate (acid sodium sulfate) , and Na 2 S0 4 , second- 
ary sodium sulfate (normal sodium sulfate). The sul- 
fates of the metals form a large class of compounds which 
vary in chemical and physical properties according to the 
metal that is present. As a class they are fairly stable 
compounds. Some, as sodium and potassium sulfates, 
are soluble ; others, as calcium sulfate, are sparingly 
so, while barium sulfate is one of the most insoluble sub- 
stances in nature. Many of the sulfates contain water of 
crystallization. Calcium and potassium sulfates are valu- 
able as fertilizers, and copper sulfate is used as a fungicide. 
120. Sulfids. — Sulfids are compounds of the metals 
with sulfur, as K 2 S, FeS, and CuS. When a sulfid, as 
FeS, is treated with a dilute acid, H 2 S, hydrogen sulfid, 
is liberated. FeS + 2 HC1 = FeCl 2 + H 2 S. 
The differences in solubility and other prop- 
erties of the sulfids are taken advantage of 
in the separation and identification of metals. 
H 2 S is formed when albuminous matter, as 
the white of an egg, decays. It is also one of 
the gases given off from sewers. It is a 
poisonous, suffocating gas. 

Experiment 22. — Hydrogen sulfid. (This experi- 
ment should be performed under the hood.) Arrange 
the apparatus as shown in Fig. 44. The delivery 
tube and cork should fit tightly, and the delivery 
tube should pass into a test tube containing 10 cc. of 
Pb(N0 3 ) 2 solution. Test tubes containing 10 cc. 
respectively of NaCl and CuS0 4 solutions should be 
conveniently at hand. Place 5 grams of pulverized 
FeS in the generating test tube, add 10 cc. dilute 
HC1, and immediately connect with the delivery tube. After the 
gas has passed through the lead nitrate solution for two minutes, 
pass it through the sodium chlorid and copper sulfate solutions ; 




Fig. 44. — Hy- 
drogen sulfid 
generator. 



SULFUR AND ITS COMPOUNDS 97 

then allow a little of the gas to escape into a cylinder containing 
water. Do not permit the free gas to escape into the room. With 
NaCl no insoluble sulfid is formed. 

Questions. — (i) What is the odor of the gas ? (2) Write the 
equation for its production. (3) What was formed when the gas 
was passed into Pb(N0 3 ) 2 ? Write the reaction. (4) What was 
formed when the gas was passed through Cu(N0 3 ) 2 ? Write the 
reaction. (5) Is H 2 S soluble in water ? (6) When albumin decays, 
from what is the H 2 S produced ? (7) Why was no precipitate formed 
when the gas was passed through NaCl ? 

Problem 1. — How much H 2 S0 4 can be made from one ton of 
sulfur ? 

Problem 2. — What per cent of H 2 S0 4 is SO3 ? 

Problem 3. — How much H 2 S0 4 is required to neutralize 500 
pounds NaOH ? 



CHAPTER XV 
Silicon and its Compounds 

121. Occurrence. — Silicon is found in nature in com- 
bination with oxygen as silica, Si0 2 ; and with oxygen 
and the metals as silicates. It is never free, but always in 
combination with other elements. Next to oxygen it is 
the most abundant element in nature. In the form 
of silicates it is the basis of the composition of nearly 
all rocks, and in the soil Si0 2 is present to the extent of 
from 60 to 90 per cent. It is in the ash of plants, and, to 
a slight extent, in animal bodies. 

122. Preparation and Properties. — Silicon is separated 
from its compounds with difficulty. By treatment in an 

electric furnace, quartz, or Si0 2 , is reduced. 
Like carbon, silicon has crystalline and 
amorphous forms. Pure quartz, Si0 2 , and 
other forms of silicon, are insoluble in 
nitric, hydrochloric, and sulfuric acids. 
When acted upon by hydrofluoric acid, 
silicon tetrafluorid, a gas, is formed. Si0 2 

Fig. 45. -Quartz + H p = Si p 4 _j_ 2 j^Q H p is used for 
crystal. . . 

the decomposition of silicates. 

123. Silicic Acid. — When Si0 2 is fused with hydroxids 
or carbonates of potassium or sodium, potassium or 
sodium silicate is obtained : 

Si0 2 + K0CO3 = K 2 Si0 3 + C0 2 . 
Si0 2 + 4 KOH = K 4 Si0 4 + 2 H 2 0. 
98 




SILICON AND ITS COMPOUNDS 



99 



The silicates of potassium and sodium are soluble in 
water, and are commonly called water-glass. Some of 
the silicates are soluble in acids, but most of them are 
insoluble complex compounds difficult to decompose. 

When K 4 Si0 4 is treated with HC1, a gelatinous mass 
containing silicic acid is obtained : K 4 Si0 4 + 4 HO = 
H 4 Si0 4 + 4 KC1. 

H 4 Si0 4 is normal silicic acid. Upon exposure to the 
air it loses a molecule of water and forms ordinary silicic 
acid, H 2 Si0 3 , which is decomposed by heat and in the 
presence of acids forms H 2 and Si0 2 . 

In addition to the two silicic acids, H 2 Si0 3 and H 4 Si0 4 , 
there are other forms known as polysilicic acids, as : 
H 2 Si 3 7 , H 4 Si 3 8 , and H 2 Si 2 5 , obtained by removing 
water from the normal and ordinary silicic acid. 

2 H 2 Si0 3 = H 2 Si0 5 + H 2 0. 

3 H 4 Si0 4 = H 4 Si 3 8 + 4 H 2 0. 

124. Dialysis. — In the preparation of silicic acid, the 
process known as dialysis is employed for dissolving and 
removing the impurities. Some sub- 
stances, as NaCl and HC1, dissolve and 
readily pass through animal membrane ; 
these are called crystalloids, while 
bodies like silicic acid, which do not 
penetrate animal membrane, or do so 
very slowly, are called colloids. The 
removal of the HC1 from the solution 
containing the gelatinous silicic acid is 
accomplished by means of the dialyzer, Fig. 46. This 
property of materials, readily or slowly to diffuse through 
animal membrane, is a physical characteristic, and is occa- 
sionally made use of for washing and separating compounds. 




Fig. 46. — Dialyzer. 



IOO AGRICULTURAL CHEMISTRY 

125. Silicates. — Since silican forms such a variety of 
acids, the number of silicates found in nature is very- 
large. The hydrogen atoms of silicic acid can be re- 
placed with different metals, forming double salts, as 
AlKSisOs, which is feldspar, or the double salt of trisilicic 
acid, H 4 Si 3 8 . This renders the composition of the sili- 
cates very complex. Many of the silicates contain also 
water of hydration as part of the molecule ; as aluminum 
silicate, Al 4 (Si0 4 )3 . H 2 0. Since rocks are composed mainly 
of silicates, and soils are formed from the decay of rocks, 
it follows that soils are practically a mechanical mixture 
of silicates with small amounts of other compounds. 
Hence, the importance of silicic acid and the silicates in 
agriculture. Unfortunately the structure and composi- 
tion of the silicates have not been determined as completely 
as of other salts and acids. Pure clay is aluminum 
silicate, formed from the disintegration of feldspar rock, 
a double silicate of potassium and aluminum. Mica, 
hornblende, and zeolites are all complex forms of 
silicates. 

126. Importance of Compounds of Silicon. — The com- 
pounds of silicon, as silicon dioxid, SiC>2, and of the sili- 
cates, are used in the manufacture of glass, porcelain, and 
brick. The element itself takes no direct part in animal 
or plant life, but indirectly is important, for it is in com- 
bination with many elements which serve as plant food. 
Some of the simpler and more soluble silicates are capable 
of being acted upon by decaying animal and vegetable 
matter and undergoing chemical changes which prepare 
them for plant food. Since silicon forms the principal 
acid element which enters into the composition of rocks, 
soils, building stones, glass, brick, and porcelain, and is 
associated with the elements in the soil which serve 



SILICON AND ITS COMPOUNDS IOI 

as plant food, it follows that it is an important element in 
industrial operations and in agriculture. 

Experiment 23. — To about 5 cc. of sodium silicate in a test tube 
add a few drops of HC1 and observe the result. Then add NaOH 
and observe the result. Add more HO, and evaporate the material 
to dryness in the evaporating dish. When cool, test the solubility 
of the residue in water. 

Questions. — (1) What was formed when HC1 was added to so- 
dium silicate ? Write the reaction. (2) What was the appearance 
of the product ? (3) What effect did the NaOH have, and what 
was formed ? (4) What was formed when the material was evapo- 
rated to dryness ? (5) What can you say as to the solubility of the 
product ? 

Problem 1. — What per cent of Si0 2 in clay, Al 4 (Si0 4 )3 . H 2 ? 

Problem 2. — How much silicic acid is formed when 10 grams of 
HC1 act upon K 4 Si0 4 ? 



CHAPTER XVI 

Oxids of Carbon, Carbonates, and Carbon 
Compounds 

127. Carbon Dioxid. — Carbon dioxid is obtained from 
the combustion of carbon and also from the treatment of 
a carbonate with an acid. A carbonate is a salt of car- 
bonic acid, M2CO3, in which M represents any mono- 
valent metal, as K or Na. Calcium carbonate, CaCC^, is 
the most abundant carbonate found in nature. When a 
carbonate is treated with an acid, CO2 is liberated, and a 
salt is formed, as 

CaCOs + 2 HC1 = CaCl 2 + C0 2 + H 2 0. 

Experiment 24. — Preparation of carbon dioxid. Arrange the 
apparatus as for the preparation of hydrogen. Put 10 grams of 
marble, CaC0 3 , into the Woulff bottle, and sufficient water to cover 
the end of the thistle tube. Fill 2 or 3 cylinders with water for 
collecting the gas, which is only slightly soluble in water, then add 
slowly, through the thistle tube, about 20 cc. concentrated HC1. 
Allow a little of the first gas generated to escape into the room and 
then collect 2 or 3 cylinders of C0 2 . Remove the cylinders from 
the pneumatic trough and place them on the desk, right side up. 
Now remove the delivery tube from the pneumatic trough and 
allow the gas to pass into a test tube containing about 10 cc. of 
clear lime water, Ca(OH) 2 . If necessary, add through the thistle 
tube a little more acid to the generator. Observe the white precipi- 
tate formed in the test tube. Let the gas pass through the lime 
water for several minutes, until the solution becomes clear. Now 
boil the solution and observe the reappearance of the white precipi- 
tate. Test some of the escaping gas with a burning splinter. Pour 
a receiver of the gas over a candle or a low gas flame, and observe 

102 



OXIDS OF CARBON, CARBONATES, ETC. IO3 

the result. Thrust a burning splinter into a cylinder of CO2. Ob- 
serve the result. Add 5 cc. water to the cylinder in which the 
splinter was placed, and then a little lime water ; shake, and observe 
the result. 

Questions. — (1) Write the reaction for the preparation of CO2. 
(2) What is a carbonate? (3) Is CaC0 3 soluble in pure water? 
(4) Is it soluble in water containing C0 2 ? (5) What caused the 
precipitate to from when the C0 2 gas was passed through the lime 
water ? (6) What is this precipitate ? Write the reaction. 
(7) What caused this precipitate to disappear when more gas was 
passed through the solution ? (8) What caused it to reappear 
when the solution was boiled ? (9) What caused the candle to be 
extinguished when a receiver of C0 2 was poured over the flame ? 
(10) O is a supporter of combustion ; C0 2 contains O ; why does 
C0 2 not support combustion ? (11) Is C0 2 a heavy or a light gas, 
and what tests indicate that it is heavy or light ? (12) What other 
carbonate could be used for making C0 2 ? (13) What other acid 
could be used for making CO2 ? 

128. Carbon Monoxid. — Carbon monoxid is formed 
when carbon is only partially oxidized because of an in- 
sufficient supply of air. In a coal stove, for example, 
there is not a perfect supply of air in the interior of the 
burning mass ; carbon monoxid is formed there and passes 
to the surface, where it burns as a blue flame. If the 
draft is imperfect, a large amount of carbon monoxid is 
formed. When a coal stove gives off gas, the carbon 
monoxid is not oxidized, but is thrown into the room. 
Carbon monoxid is a light, colorless, combustible, poison- 
ous gas, and can be produced by subjecting highly heated 
carbon to the action of steam. The reaction is C + 
H 2 = CO + 2 H. Both CO and H are combustible, 
and when they are enriched by some of the hydrocarbons, 
thus introducing materials that give light when burned, 
they may be used for illuminating purposes, and the 
product is called water gas. Carbon monoxid is pro- 



104 AGRICULTURAL CHEMISTRY 

duced in furnaces from the coke which is mixed with ore, 
and in the smelting and refining of ores, it is an important 
reducing agent ; in fact, the main reducing agent of the 
blast furnace. 

129. Marsh Gas (Methane, CH 4 ). — When vegetable 
matter decays under water, where the supply of air is 
incomplete, methane, CH 4 , is one of the products formed. 
It is given off in bubbles from the surface of stagnant 
pools. It often collects in coal mines, and is there called 
fire damp. CH 4 can be prepared in the laboratory in a 
number of ways, and is a colorless, combustible gas, 
which with air forms an explosive mixture. 

130. Hydrocarbons. — A compound, as methane, com- 
posed of hydrogen and carbon is called a hydrocarbon. 
There are a large number of such compounds, forming 
series in which the members differ from one another 
in composition by a definite number of C and H atoms, 
as methane, CH 4 , and ethane, C 2 H 6 . The 'next mem- 
ber is propane, C 3 H 8 ; CH 2 being the common difference 
between the members of this series. By oxidation, re- 
duction, and substitution, in which a part of the H is re- 
placed with equivalent radicals, a large number of de- 
rivatives, as alcohols, aldehydes, ethers, and organic 
acids, are formed. 

131. Petroleum. — Petroleum is an oily liquid obtained 
in some parts of the world by boring wells into the rock 
strata, where it is found as a natural product. It is 
a mechanical mixture of various liquid and solid hydro- 
carbons, often accompanied with gaseous hydrocarbons. 
The hydrocarbons distilled at low temperature, ranging 
from 8° to 68° C, are the gasoline and benzene products, 
while those which distil between 175 and 215 C. are the 
various grades of kerosene. In the preparation of gaso- 



OXIDS OF CARBON, CARBONATES, ETC. 



I05 



line, benzene, and kerosene, the separation of the various 
grades of hydrocarbons is not complete ; kerosene, for 
example, may contain traces 
of gasoline or paraffin prod- 
ucts. Kerosene should have 
a flashing point not below 
44 C. (in° F.), in order to 
render it safe for illuminating 
purposes. The flashing point 
of kerosene may be approxi- 
mately determined in the 
following way : 

Experiment 25. — Testing kero- 
sene. Pour into a small porcelain 
crucible some kerosene ; place the 
crucible upon a water bath, and 
suspend a thermometer in the 
kerosene. Do not allow the water 
in the bath to come in contact with 
the crucible or the thermometer to 
touch the bottom. Cautiously 
heat the water until the ther- 
mometer registers 40 C, then re- 
move the lamp and draw a lighted 
match across the surface of the 
kerosene. If it flashes, note its 
temperature ; do not let it burn ; 
should this occur, remove the 
thermometer and cover the cru- 
cible. If the kerosene does not 
flash, repeat the test, and if nec- 
essary apply more heat until the 
flashing point is reached. Calculate the corresponding tempera- 
ture on the Fahrenheit scale. 





Fig. 47. — Testing kerosene. 



132. Use of Gasoline. — Gasoline is safe for use as a 
fuel, provided precautions are observed: (1) Never use 



io6 



AGRICULTURAL CHEMISTRY 



a gasoline stove when there is but little gasoline in the 
tank, because the last gas generated is mixed with air, 
and is liable to form an explosive mixture. (2) All 
joints and connections about the stove should be tight 
to prevent escape of gasoline into the air. Lack of care 
in this respect is the most frequent cause of fires. (3) The 
gasoline can should be well corked and stored in a cool 
place. (4) The stove should be kept clean, and no de- 
posit of carbon should be allowed to collect upon the 
burners. (5) Do not fill tank while stove is lighted. 

133. Illuminating Gas. — Illuminating gas is made from 
soft coal and petroleum by destructive distillation. The 
gases formed are washed and separated from ammonia 




Fig. 48. — Illuminating gas plant for producing gas from gasoline. A, weight to ai 
pump, B. D, carburetor or generating tank into which air is forced. 

and coal tar, and consist of various hydrocarbons which 
are used for illuminating purposes. The coal, after being 
deprived of its gaseous products, is converted into coke, 



OXIDS OF CARBON, CARBONATES, ETC. 107 

which bears the same relation to coal which charcoal bears 
to wood. Ammonia and coal tar are recovered as by- 
products. Various coloring matters are made from 
coal tar. 

If air is forced through gasoline in an inclosed chamber, 
or if gasoline is vaporized, it will burn like ordinary coal 
gas. Gasoline can be vaporized on a small scale, and 
machines suitable for the purpose are made for illuminat- 
ing dwellings. Five gallons of gasoline will produce about 
1000 feet of gas or vapor. The illuminating power of 
gas, and of flames in general, is expressed in terms of 
candle power. A sixteen candle-power light is one that 
gives sixteen times as much light as a standard candle, 
composed of spermaceti, and burned at the rate of 120 
grains per hour, the comparison being made by means of 
a photometer. In some localities, hydrocarbons, due to 
decomposition of organic matter, are given off from the 
earth as natural gas in amounts sufficient to be used for 
illuminating and fuel purposes. 

134. Mineral Oils. — The heavier products obtained in 
the distillation of petroleum, after removal of the gasoline, 
benzene, and kerosene, are used for lubricating purposes, 
and are called mineral oils. They have a boiling point 
from 250 to 350 C. 

135. Oil of Turpentine (Ci Hi 6 ). — Oil of turpentine is 
obtained by distilling the resinous material which exudes 
from incisions in certain species of pines. Resin is ob- 
tained in the retorts. Oil of turpentine is inflammable, 
and dissolves readily in ether, alcohol, and naphtha. It 
is a valuable solvent, extensively used in the preparation 
of varnishes and paints, and as a solvent for caoutchouc. 
Turpentine belongs to the class of compounds known as 
essential oils. 



108 AGRICULTURAL CHEMISTRY 

136. Creosote. — When wood tar is distilled, various 
products are obtained which, after treatment with chemi- 
cals for purification, are called wood-tar creosote. This 
is a yellowish liquid with a smoky odor. It is a power- 
ful antiseptic, and is the preservative employed in the 
preparation of " smoked meats," as hams and fish. It 
has no marked action on albuminous matter, and in small 
amounts is not poisonous. Because of its antiseptic 
powers, wood creosote is used for the preservation of 
wood, as it prevents decay. When some kinds of wood, 
as beech wood, are burned, the wood tar condenses in 
the chimney. 

137. Benzene or Benzol (C 6 H 6 ). — When coal tar, ob- 
tained in the manufacture of illuminating gas, is sub- 
jected to fractional distillation, commercial products are 
obtained known as coal tar, naphtha, middle oil, heavy 
oil, anthracene oil, and pitch or artificial asphaltum. 
The naphtha or light oil consists of a mixture of hydrocar- 
bons, benzene being among the number. Benzene is 
used as a solvent for fatty bodies. It is very inflam- 
mable. 

138. Aliphatic and Aromatic Series of Compounds. — 
In organic chemistry benzene occupies an important posi- 
tion, as the direct treatment of benzene and its deriva- 
tives produces the aromatic series of compounds, which 
form one of the two main divisions of the subject. The 
other series is obtained from methane and its derivatives, 
and constitutes the aliphatic series. The alcohols, ethers, 
glycerides, fatty acids, organic acids, carbohydrates, and 
amids are members of the aliphatic series, while essen- 
tial oils, coloring matters, and mixed nitrogenous 
compounds are members of the aromatic series. In or- 
ganic chemistry a study is made of the formation, rela- 



OXIDS OF CARBON, CARBONATES, ETC. IO9 

tionship, structure, and properties of all these compounds. 
Hence the importance of this branch of chemistry. 

139. Carbon Disulfid. — With sulfur, carbon forms car- 
bon disulnd, CS 2 , a clear liquid with a characteristic odor. 
It readily burns and is easily vaporized. It is a solvent 
for fats, resins, sulfur, and iodin, and is used for the 
destruction of insects, particularly those infesting 
grains, and for killing small burrowing animals, as 
gophers. 

140. Cyanids. — In the presence of metals carbon unites 
indirectly with nitrogen, forming cyanids, as KCN. When 
mercuric cyanid is heated, cyanogen gas and metallic 
mercury are formed : Hg(CN) 2 = Hg + 2 CN. Cyano- 
gen and the cyanids are very poisonous. With H, cyano- 
gen forms hydrocyanic acid (prussic acid), which is used 
for the destruction of scale insects and in the preparation 
of pigments. Traces of this compound are found in a 
few plants ; some owe their poisonous properties to its 
presence in excessive amounts. 

141. Carbids. — With some of the metals, notably cal- 
cium, carbon forms carbids, as CaC 2 which is produced 
by the fusion of coke and limestone in electric furnaces. 
In the presence of water CaC 2 is decomposed, forming 
acetylene gas, C 2 H 2 , and calcium hydroxid. 

CaC 2 + 2 H 2 = C 2 H 2 + Ca(OH) 2 . 

Acetylene generators are made for illuminating dwell- 
ings. Acetylene, like all gaseous hydrocarbons, as 
methane and benzene, forms an explosive mixture with 
oxygen. All illuminating gases should be dealt with as 
highly combustible and explosive materials. 

142. Fuels. — There are three forms of fuel: (1) gas, 
(2) liquid, and (3) solid. Natural gas, coal gas, and gas 



IIO AGRICULTURAL CHEMISTRY 

generated from gasoline and naphtha are the principal 
forms of gas fuel ; kerosene, gasoline, and crude petro- 
leum are liquid fuels ; while coal, coke, lignite, peat, and 
wood are the chief forms of solid fuel. The composition 
of coal, coke, lignite, and peat is discussed in Chapter V. 
Wood is composed largely of cellulose, and contains, when 
dry, about 50 per cent carbon, 6 per cent hydrogen, and 
43 to 44 per cent oxygen. Air-dried wood contains from 
10 to 15 per cent moisture. Different kinds of wood 
vary in density between wide limits ; for example, a 
cord of dry pine weighs about 3000 pounds, while a cord 
of dry maple or other hard wood weighs from 4500 to 
5000 pounds, or more. Hence the same volume (as a 
cord) of soft wood yields less total heat than a cord of 
hard wood, but a pound of the different kinds of wood 
of equal moisture content gives nearly the same amount 
of heat. The amount of heat which a material produces 
when burned is measured in the calorimeter, and is given 
in terms of calories or heat units. A calorie is the heat 
required to raise the temperature of 1 kilo of water 1 
centigrade degree. The presence of water in fuels generally 
lowers the caloric value, because it requires heat to 
evaporate and expel as steam the moisture before com- 
bustion can take place. At a high temperature (above 
noo° C.) the water in fuel is converted into com- 
bustible gases by the action of heated carbon, as explained 
in Section 128, in which case the loss in fuel value is 
reduced to a minimum. 

143. Comparative Value of Fuels. — The heat-pro- 
ducing value of fuels is also expressed as British thermal 
units, B. T. U., the heat required to raise 1 pound of water 
i° F. B. T. U. per pound are changed to calories per kilo 
by dividing the number of B. T. U. by 1.8. 



OXIDS OF CARBON, CARBONATES, ETC. Ill 

B.T.U. 
Hard coal 13,000 

Soft coal, Hocking 1 1,800 

Soft coal, Pocahontas 13,000 

Soft coal, Splint 1 2,500 

Lignite with 30 per cent water 7,000 

144. Foods. — The materials used as human and animal 
foods are mechanical mixtures of various organic com- 
pounds, as starch, sugar, fat, albumin, etc., together 
with various mineral salts. The composition of the or- 
ganic compounds of foods forms a part of the study of 
organic chemistry, while their economic value and the uses 
made of them by the body are studied in physiological 
chemistry. Knowledge in regard to the composition and 
uses of foods, particularly of human foods, is somewhat 
limited, although along this line many facts and laws of 
economic and sanitary importance have been discovered. 
The subject of foods is treated more fully in the chapters 
relating to the chemistry of foods. 

Vegetable foods and fuels are alike in chemical com- 
position, and serve somewhat the same functions, but 
in different ways. Food is used as fuel by the body, 
and also for the renewal of old and the production of new 
tissues. The heat produced from food is transformed into 
muscular and other forms of energy ; the heat from the 
combustion of fuel is converted into chemical energy, 
which is utilized for mechanical purposes. 

145. Production of Organic Compounds in Plants. — 
The carbon dioxid of the air is the source of the carbon 
used by plants for the production of the various organic 
compounds found in vegetable substances, and since 
about 50 per cent of the ash-free tissue of plants is carbon, 
it follows that the carbon dioxid of the air is an important 
factor in plant growth. Hydrogen and oxygen are 



112 



AGRICULTURAL CHEMISTRY 



obtained from the water of the soil which is received from 
the air. The production of the various organic com- 
pounds of plants takes place in the cells of the leaves 
and is the result of chemical changes induced by life 



Plant food from air 




V>7-/- , /-'/^f7 



plant FOOD from soil 

INCRal CiO SO, 
MATTER P,0, N»,0 
M$0 CI 



Fig. 49. — Production of organic compounds in plants, 
showing sources of plant food. 

processes. In order to promote cell activity, sunlight 
and a suitable temperature are necessary. The sun's rays 
take an important part in promoting chemical changes 
in the leaves of plants. In addition to carbon dioxid, 
water, heat, and sunlight, various mineral elements 
in the form of compounds of potassium, calcium, phos- 
phorus, nitrogen, iron, magnesia, sulfur, and possibly 
a few others are required as plant food. Without these 
essential elements and requisite conditions, the growth 
of crops cannot take place. It often happens that soils 
are unproductive because of the absence, in available 



OXIDS OF CARBON, CARBONATES, ETC. 



113 



ss 



;3 



»* 
■& 







form, of some of the elements essential for plant life. 
The production in the leaves of plants of the various or- 
ganic compounds, as cellulose, 
starch, sugar, fat, albumin, etc., 
and a few of the complex chemi- 
cal changes which take place, are 
discussed in the second part of this 
work. 

146. Decay of Organic Com- 
pounds. — All organic compounds, 
particularly those found in the 
tissues of plants and used for food, 
are subject to the chemical change 
commonly called decay. Such 
change is nearly always produced 
as the result either of the action F i?- s ° 
of organized ferments, or of the 
chemical products known as chem- 
ical or soluble ferments. Fermen- 
tation changes and decay take place whenever cell activity 
becomes feeble or ceases ; then the material becomes food 
for microorganisms. Many chemical changes occur as the 
result of fermentation ; some of these are necessary in plant 
and animal nutrition. If the chemical changes, coordinate 
with fermentation, are uninterrupted, the organic materials 
are decomposed until carbon dioxid, water, ammonia 
gas, and hydrogen sulfid are obtained as the final products, 
and the mineral matter combined and associated with 
the organic matter is left as non- volatile material. In 
economic agriculture, it is the aim to conserve and return 
to the soil the essential elements, as nitrogen, potassium, 
phosphorus, and calcium, which are frequently unavail- 
able or present in soils in scant amounts, so that the 
1 






Decay of wood. 
Note that the decay is more 
rapid near the moist surface 
where the supply of air is 
greater. 



114 AGRICULTURAL CHEMISTRY 

fertility will not be impaired. The elements in plant and 
animal bodies pass through a cycle of chemical changes ; 
they are never lost to nature, but appear in different 
chemical compounds, as exemplified by the law of inde- 

Ostructibility of matter. 
A. Elements of plant growth in soil 
B and air. 
B. Elements from soil and air elabo- 
rated into plant tissue. 
A C. Elements in plant tissue elabo- 

Fig. si. rated into animal tissue. 

The elements in either plant or animal bodies may 
pass back to A, and then pass again through the same 
cycle of chemical changes. 



CHAPTER XVII 
Writing Equations 

147. Importance. — A chemical equation expresses con- 
cisely the changes which take place when two or more 
compounds are brought together so as to react, or when 
a material is acted upon by any agent which causes a 
chemical change. When chemical equations are under- 
stood by the student, they are of great assistance, as they 
necessitate a knowledge of the laws of valence, of the 
power of replacement, and of the properties of the ele- 
ments and their compounds. 

148. Common Errors in Writing Equations. — Some 
of the more common errors in writing equations are : 

(1) Failure to use correct formulas. 

(2) Failure to use the correct number of parts of com- 
pounds, radicals, or elements. 

(3) Failure properly to balance the equation. 

(4) Failure to form reasonable compounds or products. 

If the correct formula, or the right number of mole- 
cules, is not used, the equation is incorrect, it cannot be 
balanced, and the principle represented by the sign of 
equality is violated. There should be as many atoms of an 
element on one side of an equation as on the other. In 
order properly to balance an equation, as many mole- 
cules of the compounds on the left of the equation should 
be taken as are needed to satisfy the valences of the 
reacting elements and radicals. In the equation 

AgN0 3 + HC1 = AgCl + HNO3, 
"5 



n6 



AGRICULTURAL CHEMISTRY 



~&L 



H' 



z£ 



t 



AS' 



no: 



B 



z: 



^ 



CI' 



/ 



z: 



H' 



NO' 



Fig. 52. 



Graphic illustration of a chemical 
reaction. 



only one molecule each of AgN0 3 and HC1 is necessary, 
because all of these elements and radicals are monova- 
lent. A simple exchange takes place in which the H of 
the acid is replaced by the metal Ag. If the elements H 

and Ag were to ex- 
change places, they 
would occupy, after 
the exchange, the posi- 
tions shown on the 
right-hand side of the 
equation. This ex- 
change is represented 
graphically in Fig. 52 ; 
A represents the order before, and B after, the reaction. 
Blocks of wood marked to represent the elements and 
radicals can be used, the block marked H being replaced 
by the equivalent block marked Ag. When difficulty is 
experienced in writing chemical equations, this method 
of illustration will be found helpful. 
In an equation as 

2 NaCl + H 2 S0 4 = Na 2 S0 4 + 2 HC1, 

where both monovalent and bivalent elements and rad- 
icals are present, it is necessary to take two molecules 
of NaCl because there are two H atoms to be replaced. 
H and Na have the same valence, viz., 1, and S0 4 has a 
valence of 2. In order to obtain two atoms of Na, it is 
necessary to take 2 NaCl ; then two atoms of Na replace 
two of H. The products are Na 2 S0 4 and 2 HC1. S0 4 is 
a radical with a valence of 2 and requires 2 Na atoms in 
order to form a compound. A similar reaction is repre- 
sented graphically by the use of blocks in Fig. 53. A 
represents the arrangement before, and B the arrange- 



WRITING EQUATIONS 



117 





s 


A' 


r 

H' 


so; 


I 


H' 





^z5Z 



K 1 



K' 



no: 



no: 






B 



/ X 


K' 


so: 


K' 



ment after, the reaction. Observe that in this equation 
there is the same number of atoms of each element on 
each side of the equa- 
tion. After writing 
an equation the stu- 
dent should always ob- 
serve whether or not it 
is properly balanced, 
and that reasonable 
products are formed. 
The valences of the 
elements and radicals 
are given in Sections 
15 and 77. 

There are always 
as many parts by weight of the elements on one side of 
an equation as on the other. That is, the sum of the 
weights of the atoms and molecules on one side is equal 
to the sum of those on the other, as : 



+ 



H' 


no; 


H' 


no; 



Fig. 53. 



Graphic illustration of a chemical 
reaction. 



2 NaCl 
2 Na = 46 
2 CI =71 



+ 



+ 



117 



Na 2 S0 4 . 
2 Na = 46 
S =32 
4O =64 

142 



H 2 S0 4 = 2 HC1 

2H = 2 2H = 2 
S =32 2 CI =71 
4 O = 64 — 

— 73 

98 

117 + 98 = 215. 73 + 142 == 215. 

In the case of trivalent and bivalent elements and radi- 
cals, as in the reaction between H3PO4 and Ca(OH) 2 , it 
is necessary to take 2 H3PO4 and 3 Ca(OH) 2 , in order to 
make the equation balance. The Ca and H atoms ex- 
change places ; there are three H atoms to be replaced. 
Ca has a valence of 2 ; 1 Ca cannot replace 3 H, but 



Il8 AGRICULTURAL CHEMISTRY 

6 H(2 H3) can be replaced by 3 Ca, because 2H3 has a total 
valence of 6 and so has 3 Ca. 

2 H3PO4 + 3 Ca(OH) 2 = Ca 3 (P0 4 ) 2 + 6 H 2 0. 

3 Ca atoms replace the 2 H 3 and form Ca3(P0 4 ) 2 , a bal- 
anced compound, because P0 4 is a radical having a valence 
of 3, and if taken twice, its total valence is 6, with which 
3 Ca atoms can combine. The remaining H and atoms 
form 6 H 2 0. 

149. Impossible Reactions. — Not all chemical com- 
pounds when brought together give a chemical reaction. 
Whether or not a reaction takes place can be determined 
only after a careful study of the elements and their prop- 
erties ; this often involves a more exhaustive knowledge 
of chemistry than can be obtained from an elementary 
study of the subject. 

In the case of BaS0 4 + 2 HC1, no reaction can take 
place, although an apparently correct reaction can be 
written : 

BaS0 4 + 2 HC1 = BaCl 2 + H 2 S0 4 . 

This is because BaS0 4 and HC1 are the products of the 
reaction 

BaCl 2 + H 2 S0 4 = BaS0 4 + 2 HC1. 

In the equations given at the end of this chapter a reac- 
tion takes place in each case. 

150. A Knowledge of Reacting Compounds and Prod- 
ucts Necessary. — In order that the writing of chemical 
equations may become more than a mere mechanical oper- 
ation, the student should study the character and prop- 
erties of the compounds used and of the products formed. 
If one of the compounds is an acid and the other a base, 
the subject of neutralization is illustrated. If one of the 



WRITING EQUATIONS HO 

compounds is an acid and the other a metal, the re- 
placement of the H of the acid occurs. Should one of 
the compounds be an acid and the other a salt, an equiva- 
lent amount of the H is replaced by the metal or basic 
element of the salt. Other principles and laws should 
be observed by the student in writing equations. The 
character of the compounds, as acid, base, or salt, with 
their names, forms a part of equation work, which is an 
essential feature of elementary chemistry. 

151. Equations for Classroom Work. — The student 
should write the following equations : 

1. CaCl 2 + Na 2 C0 3 = 

2. CaCl 2 + Na 2 S0 4 = 

3. Ca(OH) 2 + H 2 S0 4 = 

4. CaC0 3 + HC1 = 

5. MgC0 3 + HC1 = 

6. KNO3 + H0SO4 = 

7. CaCl 2 + Na 3 (P0 4 ) = 

8. Pb(N0 3 ) 2 + 2 HC1 = 

9. AICI3 + NH4OH = 

10. Ba(OH) 2 + H 2 S0 4 = 

11. BaCl 2 + H 2 S0 4 = 

12. Pb(N0 3 ) 2 + H 2 S0 4 = 

13. Na 2 C0 3 + H 2 S0 4 = 

14. Na 3 P0 4 + H 2 S0 4 = 

15. Ca(OH) 2 + Na 2 S0 4 = 

16. Fe(OH) 3 + H 2 S0 4 = 

17. (NH 4 ) 2 S0 4 + Ca(OH) 2 = 

18. NH 4 N0 3 + H 2 S0 4 = 

19. (NH 4 ) 2 C0 3 + HC1 = 

20. NH 4 C1 + H 2 S0 4 = 

21. NH 4 C1 + Ca(OH) 2 = 



I20 AGRICULTURAL CHEMISTRY 

2 2. NH4CI + NaOH = 

23 . NH4CI + Ba(OH) 2 = 

24. NH4NO3 + Ca(OH) 2 = 

25. NH4OH + HC1 = 

26. NH4NO3 + KOH = 

27. FeCl 2 + NaOH = 

28. FeCl 2 + NH4OH = 

29. AgCl + H 2 S = 

30. Na 2 C0 3 + Ba(OH) 2 = 

31. Na 2 C0 3 + HC1 = 

32. NaOH + FeCl 2 = 

33. AgN0 3 + NaCl = 

34. AgN0 3 + HC1 = 

35. Ca 3 (P0 4 ) 2 + 3H 2 S0 4 = 

36. CaC0 3 + heat = 

37. CaO + C0 2 = 

38. Ca(OH) 2 + C0 2 = 

39. K + H 2 = 

40. A1K(S0 4 ) 2 + 3 KOH = 

41. A1NH 4 (S0 4 ) 2 + NH4OH = 

42. CaCl 2 + (NH 4 ) 2 C0 3 = 

43. CaCl 2 + H 2 S0 4 = 

44. Na 2 Si0 3 + HC1 = 

45. CaSi0 3 + Na 2 C0 3 = 

46. C + CuO = 

47. CuCl 2 -f H 2 S = 

48. C 6 Hi O 5 + 12 O = 

49. AICI3 + H 3 P0 4 = 

50. AlCls + NH4OH = 



CHAPTER XVIII 
Potassium, Sodium, and their Compounds 

152. Occurrence of Potassium. — Potassium is found in 
nature largely in combination with silicon and other ele- 
ments forming silicates, which undergo slow disintegra- 
tion with liberation of potassium salts which become food 
for plants. Potassium is in the ash of all plants and food 
materials and is one of the elements required by crops. 
In some " alkali " soils, small amounts are found in the 
form of potassium salts. Deposits of various double 
salts of potassium, supposed to have been formed by 
crystallization from sea water, are found at Stassfurt in 
Prussia, and are commonly known as Stassfurt salts. 
These are the chief sources of the potassium compounds, 
some of which are extensively used for fertilizer. 

The element potassium is most typical of all the base 
elements as a class. It is never found in nature in a 
free state, but always in combination with other elements, 
from which it is separated with difficulty. It is a light 
substance with a metallic luster, and in the laboratory 
is kept from contact with air and water, with which it 
readily reacts. 

153. Potassium Hydroxid. — This is a strong basic 
compound extensively used in the laboratory and in 
manufacturing operations. It is prepared by treating 
K2CO3 with Ca(OH) 2 , the reaction being K 2 C0 3 + Ca(OH) 2 
= CaC0 3 + 2 KOH. CaC0 3 is insoluble and can 
be separated by filtering from KOH, which is soluble. 

121 



122 



AGRICULTURAL CHEMISTRY 




Fig. 54. — Prepara- 
tion of KOH. 



KOH, commonly called caustic potash, is a white, brittle 
substance which readily absorbs moisture and carbon 
dioxid from the air. 

Experiment 26. — Preparation of KOH. Dissolve 5 grams po- 
tassium carbonate, K 2 C0 3 , in an evaporating dish containing 15 cc. 
of water. Add a mixture of 3 grams Ba(OH) 2 
and 10 cc. of water. Heat on the sand bath 
for five minutes. Filter off the solution. Ob- 
serve the precipitate. Evaporate some of the 
solution to dryness in the evaporator. 

Questions. — (1) Write the reaction which 
takes place between K 2 C0 3 and Ba(OH) 2 . 
(2) What is the insoluble white material left 
on the filter paper ? (3) Is the KOH soluble 
or insoluble ? (4) What other material could 
be used in place of Ba(OH) 2 ? (5) If Na 2 C0 3 
were used instead of K 2 C0 3 , what product would 
be formed ? Write the reaction. (6) What 
reaction does K 2 C0 3 give with litmus paper ? 
(7) What reaction does NaOH give ? (8) What are some of 
the uses made of KOH ? (9) What would result if the KOH in 
the evaporator were left exposed to the air for a day or more ? 

154. Potassium Nitrate. — This salt is found in small 
amounts in fertile soils where conditions have been favor- 
able for nitrification processes (see Section 92). It is 
extensively used in the arts, and is prepared from sodium 
nitrate deposits which occur as natural products known 
as Chile saltpeter. It is an oxidizing agent and is one 
of the ingredients of gunpowder, which is a mixture of 
sulfur, carbon, and potassium nitrate. Potassium nitrate, 
in small amounts, is occasionally used for the preserva- 
tion of meats. 

155. Potassium Carbonate. — When wood ashes are 
leached, potassium carbonate is the chief alkaline salt 
extracted, and this product is called potash, which, by 



POTASSIUM, SODIUM, ETC. 1 23 

the removal of impurities, furnishes pure K 2 C0 3 . Potas- 
sium carbonate is prepared from the chlorid in the same 
way that sodium carbonate is prepared from its chlorid 
as explained in Section 162. 

156. Potassium Chlorate is prepared by the action of 
chlorin gas upon potassium hydrate. It is used in the 
laboratory as an oxidizing agent, and for the preparation 
of oxygen. It is one of the ingredients of safety matches. 

157. Potassium Sulfate is found in nature in the form 
of double salts, in the Stassfurt deposits and elsewhere. 
It is employed in the preparation of alum and other com- 
pounds. There are two sulfates of potassium : primary or 
acid potassium sulfate, KHS0 4 , and secondary or normal 
potassium sulfate, K2SO4. 

158. Miscellaneous Potassium Salts. — Potassium 
forms a large number of salts, as KC1, KBr, KF, Kl, 
KCN, K 2 S, KN0 2 , many of which are very valuable 
in medicine, in the arts as photography, and in the labora- 
tory for the preparation of other compounds. The salts 
of potassium vary in chemical and physical properties 
according to the acid elements or radicals with which the 
potassium is combined. All of the common salts of potas- 
sium, except the double silicates, are soluble in water. 

159. Occurrence of Sodium. — Sodium and potassium 
are very much alike in general properties, and form analo- 
gous salts and compounds. Sodium is not so strong a 
type of basic element as is potassium, and can be sepa- 
rated from its compounds more readily, although it is not 
easily replaced by other elements or by simple chemical 
forces. Sodium and its compounds are less expensive 
than potassium and its compounds. In industrial opera- 
tions sodium salts are more extensively used, but to the 
agricultural student potassium is of greater importance 



124 AGRICULTURAL CHEMISTRY 

because sodium takes little or no part in plant nutrition. 
In animal life, however, sodium chlorid plays an impor- 
tant role. Sodium is never found in nature in a free state, 
sodium chlorid being one of the most abundant of its 
salts. Sodium is also found as silicates and in small 
amounts in other forms. 

1 60. Sodium Chlorid. — Extensive deposits of this salt 
are found in nature. In some places it is mined, the prod- 
uct being known as rock salt. It is in sea water in large 
amounts, from which it is occasionally obtained in an 
impure form along with a number of other salts. When 
pure, sodium chlorid forms colorless, transparent cubes. 
Much commercial salt is obtained by evaporation of water 
from salt springs. In some localities, water is forced into 
and through deposits of salt, which it dissolves, and it is 
then pumped out and evaporated to dryness. Sodium 
chlorid is extensively used for the preparation of sodium 
carbonate and other compounds, as hydrochloric acid. 
It is not found to any appreciable extent in ordinary 
agricultural plants, but in some alkali plants there are 
quite large amounts. When sodium chlorid contains 
impurities, as calcium chlorid and lime salts, the material 
readily absorbs moisture from the air, while other com- 
pounds cause it to form lumps and hard cakes. Hence 
a salt which readily absorbs moisture or forms hard 
lumps is not pure. Sodium chlorid takes little or no part 
in plant life, but is necessary for animal life. 

161. Sodium Nitrate. — Extensive deposits of sodium 
nitrate are found in Peru, Chile, and other South Ameri- 
can countries. It is commonly called Chile saltpeter. 
As stated in Section 154, it is used for the preparation of 
potassium nitrate and in the manufacture of nitric acid 
and commercial fertilizers. Sodium nitrate is commer- 



POTASSIUM, SODIUM, ETC. 1 25 

cially and agriculturally an important product. The 
value of nitrogen in fertilizers is usually based upon the 
selling price of sodium nitrate. Small amounts of this 
salt, formed by the process of nitrification, are found in 
soils of high fertility. Because of its solubility, however, 
it never accumulates in soils. 

162. Sodium Carbonate. — Commercially, this salt is 
known as soda, and is one of the most useful chemicals 
manufactured. It is used in the making of soap and 
glass, and in other commercial operations. It is prepared 
by two processes, one known as Le Blanc process, and 
the other as ammonia or Solvay process. By Le Blanc 
process, it is prepared from sodium chlorid treated with 
sulfuric acid, which produces Na 2 S0 4 . 

2 NaCl + H 2 S0 4 = Na 2 S0 4 + 2 HC1. 
The sodium sulfate is heated with charcoal; which pro- 
duces sodium sulfid. 

Na 2 S0 4 + 2 C = Na 2 S + 2 C0 2 . 

When heated with calcium carbonate, sodium sulfid forms 
sodium carbonate and calcium sulfid, the latter product 
being insoluble in water, while sodium carbonate is solu- 
ble in water and hence is readily separated by filtration. 
The process of manufacture usually consists in mixing 
coal and calcium carbonate with sodium sulfate, the prod- 
uct being known as crude soda, which is refined, and from 
which calcined and crystallized soda are obtained. 

In the Solvay process, (NH 4 ) 2 C03 is employed, which 
forms, with sodium chlorid, HNaC0 3 , which when heated 
yields Na 2 C0 3 , C0 2 , and H 2 0. 

163. Sodium Hydroxid. — This base is prepared in the 
same way as KOH ; Na 2 C0 3 being used in place of K 2 C0 3 . 
NaOH is extensively used in the manufacture of soaps. 



126 



AGRICULTURAL CHEMISTRY 



164. Sodium Phosphates. — Sodium forms three phos- 
phates : primary sodium phosphate, secondary sodium 
phosphate, Na 2 HP0 4 , and tertiary or normal sodium phos- 
phate, Na 3 P0 4 . Phosphates of soda are not found to any 
appreciable extent in soils, because phosphoric acid forms, 
with iron, alumina, and calcium, which are always present, 
insoluble compounds. 

165. Miscellaneous Sodium Salts. — Like potassium, 
sodium forms a large number of salts, as Na 2 S0 4 , NaHS0 4 , 
NaBr, NaCN, Na 2 S and Na 2 0. Sodium compounds are 

all soluble except the silicates 
and a few of the more com- 
plex salts. 

As previously stated, salts 
of sodium are similar to the 
corresponding salts of potas- 
sium. The sodium com- 
pounds are among the most 
useful and important com- 
pounds found in nature. 




Experiment 27. — Fill a cylin- 
der about two thirds full of water, 
and place upon the surface of the 
water a piece of Na about half as 
large as a pea, using forceps for 
the purpose. If there is no small 
piece of Na in the bottle, one may 
be cut by means of a knife with- 
out removing the Na from the 
naphtha which surrounds it. Ob- 
serve the result when the Na is 
placed upon the water. The appa- 
ratus can be arranged and the escaping hydrogen collected as shown 
in Fig. 55. (The test tube should be filled with water and the Na 
wrapped in a piece of filter-paper.) 



Fig. 55. 



-Decomposition of water by 
the use of sodium. 



POTASSIUM, SODIUM, ETC. 1 27 

Questions.— (1) Give the reaction which takes place between Na 
and H 2 0. (2) What gas is liberated ? (3) What becomes of Na in 
the experiment ? (4) Is this product soluble or insoluble ? (5) Test 
the liquid in the cylinder with litmus paper and observe the result. 
(6) Is Na a light or heavy metal ? Why ? (7) Is it active or inert ? 
(8) Why is Na always kept in a bottle containing naphtha or kero- 
sene ? (9) Since NaCl is found in sea water, why does not Na of 
the NaCl decompose sea water as the element Na did the water in 
this experiment ? 



CHAPTER XIX 



Calcium, Magnesium, and their Compounds 

i 66. Occurrence of Calcium. — This element is found 
widely distributed in nature in the form of calcium car- 
bonate, CaC0 3 , calcium phosphate, Ca 3 (P0 4 )2, and cal- 
cium sulfate, CaSCU, and is a yellowish metal which 
readily oxidizes and decomposes water. It enters into 
the composition of both plant and animal bodies and 
takes an important part in life processes. Its compounds 
are useful in the industries, lime, cement, and mortar being 

some of the forms in 
^ which it is employed. 
Calcium is not easily 
separated from its 
compounds. 

167. Calcium Car- 
bonate. — This com- 
pound, in the form of 
limestone and 
marble, is 
found exten- 
sively. It is 
somewhat sol- 
uble in water 
charged with 
carbon dioxid, and hence many waters, as stated in Section 
65, owe their hardness to its presence. Calcium carbon- 
ate is used principally for the preparation of quicklime, 

128 




Fig. 56. 



Sec' ion of lime kiln. 



CALCIUM, MAGNESIUM, ETC. 



129 



in the manufacture of glass, and in the refining of some 
metals, where it is employed as a flux. 

168. Calcium Oxid. — When calcium carbonate is sub- 
jected to heat, as in lime kilns or specially constructed 
furnaces, the carbon dioxid is separated and the oxid 
obtained. Layers of limestone and wood are placed alter- 
nately in the lime kiln, as shown in Fig. 56. The combus- 
tion of the wood furnishes the necessary heat for the 
decomposition of the carbonate. Calcium oxid or quick- 
lime readily combines with both the carbon dioxid and the 
moisture of the air,, forming air-slaked lime. During this 
process of slaking, there is a material increase in volume, 
often resulting in the bursting of the barrels in which the 
lime is stored. Calcium oxid is used for the preparation 
of calcium hydroxid and mortar. 

169. Calcium Hydroxid. — When water is added to cal- 
cium oxid or quicklime, the material undergoes the slak- 
ing process, and calcium hydroxid, 
Ca(OH) 2 , is produced. 

CaO + H 2 = Ca(OH) 2 . 

Calcium hydroxid or slaked lime readily 

absorbs carbon dioxid from the air and 

forms calcium carbonate. Ca(OH) 2 is 

somewhat soluble in water, forming what 

is commonly called lime water. When 

carbon dioxid is passed into lime 

water, the solution becomes turbid, due 

to the formation of CaC0 3 . This 

reaction furnishes a means of testing 

for carbon dioxid. If a small amount of 

any material supposed to contain carbonates is placed 

in a test tube with a little water, and then a small glass 




w 



Fig. 57. 



13° 



AGRICULTURAL CHEMISTRY 



tube or loop tube containing a few drops of lime water 
is inserted in the test tube, after the gas is liberated by 
hydrochloric acid, the drop of lime water becomes turbid, 
due to the formation of CaC0 3 (see Fig. 57). 

170. Calcium Sulfate. — Deposits of this salt known as 
gypsum, CaS0 4 . 2 H 2 0, are found abundantly in some 
localities. Gypsum or land plaster is used as a fertilizer 
and also for the preparation of plaster of Paris. The 
" setting " of plaster of Paris is due to the fact that when 
the water of crystallization has been expelled, the sub- 
stance is again capable of taking up water, expanding, 
and forming a hard mass. 

171. Calcium Chlorid. — This salt is not found in nature 
to any appreciable extent. It is employed in the labora- 
tory in desiccators and for the drying of gases. 

172. Bleaching-powder is made by 
passing chlorin into a solution of lime 
water. The chlorin is held in chemical 
combination, forming calcium hypochlo- 
rite, Ca(C10) 2 , which readily gives up its 
chlorin and is extensively used for bleach- 
ing and disinfecting purposes, as ex- 
plained in Section 89. 

173. Calcium Phosphate. — Deposits 
of this material are found in nature 
in various physical forms as soft phos- 
phate, and in crystalline form, as apatite 

rock, see Fig. 58. Calcium phosphate is extensively used 
for the preparation of commercial fertilizers, as ex- 
plained in Section 109. 

174. Mortar. — When quicklime is slaked and mixed 
with sand, it forms at first a mechanical mixture. When 
it is placed upon the walls of buildings, a chemical change, 




Fig. 58. — Apatite 
rock. 



CALCIUM, MAGNESIUM, ETC. 131 

known as the hardening or setting process, takes place. 
When this change occurs, the moisture is expelled and 
the carbon dioxid of the air changes the calcium hydroxid 
to calcium carbonate. In the slaking of lime and the 
setting of mortar, the following reactions take place : 

(1) CaO + H 2 = Ca(OH) 2 . 

(2) Ca(OH) 2 + C0 2 = CaC0 3 . 

When magnesium carbonate and aluminum silicate are 
present, forming part of the composition of the original 
lime rock, hydraulic cement is produced, which has the 
property of setting under water. 

Experiment 28. — Testing quality of lime. Place about 40 grams 
of lime, CaO, in an evaporating dish and moisten with water warmed 
to about 350 C. Note the reaction. Good lime readily undergoes 
the slaking process. Place some of the slaked lime in a bottle, add 
about 100 cc. of distilled water, shake vigorously and leave the 
lime in contact with the water for four hours or longer, then filter 
some of the solution of lime water, and test it by forcing respired 
air through it as explained in Experiment 24. 

Place about one half gram of the slaked lime in a test tube, add 
10 cc. of water and then a few drops of HC1. When action ceases, 
add more HC1, a little at a time, and heat. The material which 
fails to dissolve usually consists of insoluble silica and clay. Lime 
of a high degree of purity contains less than 10 per cent of acid- 
insoluble impurities. 

Questions. — ( 1 ) Was any heat evolved when the lime was slaked ? 
Why ? (2) Did any noticeable change take place in volume during 
slaking? (3) What is lime water? (4) What is shown by forcing 
respired air through the lime water of the test tube ? (5) Write the 
reaction which took place. (6) Write the reaction when HC1 was 
added to Ca(OH) 2 . 

175. Glass. — Glass is a double silicate of calcium and 
sodium, produced by fusing pure sand, sodium carbonate, 
and lime. To make Bohemian or hard glass potassium 



132 AGRICULTURAL CHEMISTRY 

carbonate is substituted for the sodium salt. Other 
kinds and varieties of glass are made by introducing 
other substances and giving different mechanical treat- 
ment to the material during its preparation. 

176. Occurrence of Magnesia. — This element does not 
occur as extensively in nature as calcium, which it resem- 
bles in many respects. It is found mainly associated 
with calcium in the mineral dolomite, which is a double 
carbonate of calcium and magnesium. Magnesium is 
found in both plant and animal substances, as is calcium, 
but is separated from its compounds more readily than 
calcium. In some plants, and in some parts of the plant, 
as in the seeds of grains, it is found, more abundantly than 
calcium. It is generally considered an essential element of 
plant food. The compounds of magnesium resemble 
those of calcium in many respects, but differ materially 
from the calcium salts in both chemical and physical 
properties. 

177. Magnesium Salts. — Magnesium carbonate and 
magnesium sulfate (Epsom's salt) are among the most 
common of the magnesium compounds. Magnesium 
chlorid, MgCl 2 , and MgS0 4 are found as double salts in 
the Stassfurt deposits. Magnesium oxid is obtained by 
combustion of magnesium. Magnesium forms also other 
compounds, as nitrates, phosphates, silicates, etc. 

Experiment 2Q. — Hold a piece of magnesium ribbon about an 
inch long in the forceps and apply a lighted match to the ribbon. 
Examine the product. 

Questions. — (1) What are some of the chemical properties of the 
element as observed from this experiment ? (2) What product was 
formed ? Write the reaction. (3) Which would weigh more, the 
original magnesium ribbon or the white powder obtained from its 
combustion ? Why ? (4) Why does magnesium produce such an 
intense light ? 



CHAPTER XX 
Iron, Aluminum, and their Compounds 

178. Occurrence of Iron. — Iron is found in nature 
mainly in the form of its oxids, hematite, Fe 2 3 , and 
magnetite, Fe 3 4 . It also occurs as carbonate, FeC03, 
pyrite, FeS 2 , and brown iron ore or basic hydroxid. In 
the soil it is in combination with silicon and other elements, 
forming double silicates. It enters into the composition 
of all plant and animal bodies and has an essential part 
in plant growth and animal life. Some waters contain 
carbonate of iron which, like calcium carbonate, is soluble 
in the presence of carbon dioxid. Upon exposure to the 
air, the iron is precipitated as hydroxid, forming a brown 
deposit. Iron takes an important part in industrial 
operations, and its chemistry has been more extensively 
studied than that of any other element. 

179. Reduction of Iron Ores. — Only iron ores of high 
degree of purity are in condition, as mined, for the blast 
furnace. Magnetic iron ore is concentrated and separated 
from its impurities by magnetic concentrators. The 
blast furnace used for the production of cast iron is con- 
structed of brick ; a type of it is shown in Fig. 59. Ore, 
coke, and flux, usually limestone, are mixed in the right 
proportions and introduced into the top of the furnace. 
The flux is used to separate the impurities, forming a 
fusible slag which is largely calcium silicate. Hot air 
is forced into the furnace by means of blowing engines, 
through tuyeres. The carbon dioxid produced is first 

133 



134 



AGRICULTURAL CHEMISTRY 




Fig. 59. — Blast-furnace (after Hart). 



IRON, ALUMINUM, ETC. 135 

reduced to carbon monoxid, which passes over the heated 
ore in the upper part of the furnace, and is the main re- 
ducing agent of the blast furnace. The carbon monoxid 
given off at the top of the furnace is collected and used for 
heating the blast. The furnace is constructed to utilize 
the heat to the best advantage so the blast can act effi- 
ciently. The slag which carries a large portion of the im- 
purities of the ore, being lighter than the molten iron, 
collects on the surface and is removed from time to time. 
The molten iron is run off from the bottom of the furnace 
into molds ; iron that is produced in this way is known 
as pig iron. It contains a number of impurities, as phos- 
phorus, carbon, silicon, and sulfur. 

1 80. Wrought Iron. — Wrought iron is produced from 
cast iron by two processes: (i) puddling, which consists 
of oxidizing the impurities by means of a blast of hot 
air passed over or blown through the iron, and known as 
the Bessemer process ; and (2) cementation, by which the 
cast iron is mixed with iron ores reasonably pure and 
heated to a high temperature so that the oxygen of the 
ores may oxidize the carbon, phosphorus, and sulfur of 
the cast iron. Wrought iron is the purest commercial 
form of iron. It usually contains about 0.5 per cent 
of carbon, and melts at about 2000 C. The nature of the 
impurities determines the character of both wrought iron 
and steel, as any increase in the amount of carbon de- 
creases its malleability and other desirable properties. 

181. Steel. — This form of iron contains less carbon 
than cast iron, but more than wrought iron. It is pre- 
pared by oxidizing the impurities of iron with a blast of 
hot air. The cast iron is heated in converters and then 
there is forced through it a blast of hot air which oxidizes 
most of the impurities. By adding cast iron, steel con- 



136 



AGRICULTURAL CHEMISTRY 




IRON, ALUMINUM, ETC. 137 

taining almost any desired amount of carbon can be ob- 
tained. Iron and steel wire are made by drawing rods 
through hardened steel plates, the material being properly 
tempered during the operation. The thin coat of oxid 
formed on the surface is removed by dipping the wire 
into a bath of dilute sulfuric acid. 

182. Rusting of Iron. — Iron in all of its forms readily 
undergoes oxidation and rusting, due to the joint action 
of oxygen and water, and results in the production of 
a basic oxid of iron. When the surface of iron is pro- 
tected, as by painting, oxidation and rusting are pre- 
vented. When iron is heated to its kindling temperature, 
it readily oxidizes, as in Experiment i. In welding iron, 
oxidation is prevented as far as possible by manipulation 
and occasionally by the use of some material, as borax, 
to remove the thin coating of oxid. Iron is readily acted 
upon by all acids, forming a large number of salts. 

183. Iron Compounds. — Iron forms two series of salts : 
ferrous and ferric. Ferrous sulfate, FeS0 4 , commonly 
called copperas, is used most extensively of any of the 
iron salts, especially in the dyeing of cloth, and to some 
extent as a disinfectant. 

Experiment 30. — Dissolve 0.5 gram of ferrous sulfate in 20 cc. of 
water. Filter if the solution is not clear, and divide the filtrate 
into two portions. To the first portion, add a few drops of am- 
monium hydroxid until a precipitate is obtained. To the second 
portion, add about 5 drops of strong nitric acid. Heat to boiling ; 
when cool, add ammonia to neutralize the acid and precipitate the 
iron. Nitric acid oxidizes iron and changes it from the ferrous to the 
ferric state. Compare the two precipitates. 

Questions. (1) What was formed when NH 4 OH was added to 
FeS0 4 ? Write the reaction. (2) Give the color and other physical 
properties. (3) What change did the HN0 3 produce ? (4) What 
change did you observe in the color of the solution during the boil- 



^8 AGRICULTURAL CHEMISTRY 

ing ? (5) What was produced when NH 4 OH was added to Fe 2 (S0 4 )3 ? 
Write the reaction. (6) Give the color and some of the physical 
properties. (7) How does this last precipitate differ from the first 
one obtained ? 

Experiment 31. — Dissolve 1 gram tannic acid in 25 cc. of hot 
water. Dip a piece of cotton cloth into this solution. Dry the 
cloth and then dip it into a solution of ferrous sulfate (1 gram per 
25 cc. of water). After the cloth has dried, see if the color can be 
removed by washing. Add 5 cc. of ferrous sulfate solution to 5 cc. 
of tannic acid solution. Observe the result. The FeS0 4 forms, 
with the tannic acid, iron tannate. 

Questions. — (1) Would the FeS0 4 alone give the same color to 
the cloth ? Why ? (2) Was the color a permanent one ? (3) Tea 
contains tannic acid ; why does tea prepared in an iron kettle give 
a black infusion? (4) What was produced when the solution of 
FeS0 4 was added to the tannic acid ? 

184. Occurrence of Aluminum. — Aluminum is a gray- 
ish white metal much lighter than iron and of greater 
tensile strength, and is found mainly as one of the constitu- 
ents of clay (Al 4 (Si0 4 ) 3 + 4H2O) that is formed from the 
disintegration of feldspar, AlKSi 3 8 , a double silicate of 
potassium and aluminum. It is also found in other com- 
binations, as in mica and cryolite (Na 3 AlF 6 ), and is present 
in nearly all soils and in small amounts in plant substances, 
although it takes no part as plant food. Aluminum is 
not easily isolated from its compounds. It can be pro- 
duced by treatment of its chlorid with sodium, but is 
now extensively prepared by electrolysis. When pure, 
it is not so readily oxidized or acted upon by acids as is 
iron. Aluminum forms a large number of compounds 
and also alloys with many of the metals. 

185. Alums. — In industrial operations, alum is used 
most extensively of any of the compounds of aluminum. An 
alum is a double sulfate of aluminum. It has the general 
composition of MA1(S0 ) 2 i2 H 2 0, in which M represents 



IRON, ALUMINUM, ETC. 1 39 

any monovalent metal, as potassium. The Al can also 
be replaced by a trivalent element. Alum is used in 
the tanning of leather, in the manufacture of paper, and 
in the coloring of cloth as the basis of the mordant or 
material for making the dye permanent. Alum is 
also used occasionally in the preparation of baking 
powders. 

Experiment 32. — Add a few drops of alum solution to a test tube 
containing 5 cc. of water, and then add a few drops of tincture of 
logwood and 2 cc. (NH 4 )2C0 3 . Observe the result. Mix about 2 
grams of flour in a dish with water containing a few drops of alum. 
Add a few drops of logwood and the same amount of ammonium 
carbonate solution ; mix well, and observe the result. Repeat the 
test, using a baking powder, and test for the presence or absence 
of alum. In the presence of alum, a blue color is always obtained 
with tincture of logwood and ammonium carbonate solution. 

Experiment 33. — To a solution of egg albumin, add a few drops 
of alum solution and observe the result. 

Questions. — (1) Does the alum cause a precipitate ? (2) Of what 
is the precipitate composed ? (3) How would alum act in the diges- 
tive tract in the presence of soluble albuminous compounds ? 
(4) Why is alum an undesirable ingredient in baking powders and 
foods ? 

186. Pottery. — Pure clay or kaolin is used for the 
manufacture of the best grades of porcelain and pottery. 
The plastic clay is modeled into the desired form and then 
dipped into a bath containing feldspar and other materials 
which, when fused, form the glaze. Ordinary earthenware 
is made from impure clay which contains compounds of 
iron and other elements. Brick and tile are also made 
from clay, the physical properties, as color, hardness, 
wearing qualities, etc., depending upon the amounts 
of iron, lime, magnesia, and alkalies present. As or- 
dinarily found in the soil, clay is mechanically associated 



14 ° AGRICULTURAL CHEMISTRY 

with a large number of other substances, many of which 
contain the elements essential to plant life, as potassium 
and calcium. Pure clay itself contains no plant food 
but clay soils are usually among the most fertile because' 
along with the disintegration of feldspar and other rocks' 
various minerals that impart fertility are made available 
and are associated with the clay. 



CHAPTER XXI 

Copper, Zinc, Lead, Tin, Arsenic, Mercury, and 
their Compounds and Alloys 

187. Commercial Importance. — The compounds of 
copper, zinc, lead, tin, and arsenic, while they do not 
enter into the composition of either plant or animal 
bodies, are of value in agriculture because of their presence 
in many useful materials. 

188. Occurrence of Copper and its Metallurgy. — 
Copper is found in the free state and also in combination 
with oxygen as CuO and Cu 2 0, with sulfur as Cu 2 S, and 
with iron and sulfur as copper pyrite, Cu 2 S . Fe 2 S 3 . The 
ores of copper are first roasted, and if iron is present in 
large amounts, it is removed as a silicate. The " matte," 
as it is called, thus produced is subjected to further re- 
fining. Copper is also separated by electrolysis. 

189. Copper Sulfate. — This salt is used the most ex- 
tensively of any of the copper compounds, and is produced 
by the action of sulfuric acid upon either metallic copper 
or its sulfid. It crystallizes with 5 molecules of water of 
crystallization. It is commonly called blue vitriol, and 
is extensively used in the preparation of pigments, for the 
preservation of wood, for copper-plating, and for the treat- 
ment of fungous diseases of plants, as in the Bordeaux 
mixture, where it is the principal ingredient. 

Experiment 34. — Dissolve 6.2 grams of copper sulfate, 3.50 
grams of sodium potassium tartrate, and 2§ grams KOH in 100 cc. 
of water. This is Fehling's solution. Dissolve 0.1 gram of glucose 

141 



142 AGRICULTURAL CHEMISTRY 

in 5 cc. of water, add 5 cc. of alkaline copper sulfate solution and heat 
to boiling. Observe the brown precipitate of Cu 2 0. The amount 
of Cu 2 produced is proportional to the amount of glucose present, 
and when the work is carefully done and the copper weighed or 
determined by other means, the per cent of glucose in a material 
can be determined. A hot alkaline solution of copper sulfate 
(Fehling's solution) is reduced to CU2O in the presence of glucose 
and a few other organic compounds. 

190. Bordeaux Mixture. — In this preparation, the 
copper is present as an insoluble hydroxid. To prepare 
the Bordeaux mixture 12.5 pounds of copper sulfate 
are dissolved in about 2 gallons of hot water; 3.5 pounds 
of lime are slaked in 2 gallons of water, and strained 
into a barrel through a coarse cloth to remove any large 
pieces. The solution of copper sulfate is then poured 
into the barrel and well stirred. The reaction which 
takes place is 

Ca(OH) 2 + CuS0 4 = Cu(OH) 2 + CaS0 4 . 

In preparing the Bordeaux mixture, just sufficient 
lime should be used to combine with all of the copper. 

191. Occurrence of Zinc. — This metal is found in 
nature mainly as zinc carbonate, ZnC03, and to a less ex- 
tent as the sulfid. Small amounts are in other forms. 
Zinc is separated from its ores by roasting with charcoal, 
which volatilizes. It is then collected as zinc dust, purified, 
and prepared for various purposes. 

192. Compounds of Zinc. — Zinc forms a large number 
of compounds, as ZnCl 2 , Zn(OH) 2 , ZnS, and ZnSCV 
Some of the zinc salts are used in the preparation of 
paints, while the metal itself is employed in many ways, 
as in making alloys, solder, and galvanized iron. 

193. Galvanized Iron. — Iron is galvanized by being 
covered with a layer of zinc. Galvanized iron is exten- 



COPPER, ZINC, LEAD, ETC. 143 

sively used for water pipes because it does not rust so 
readily as ordinary iron. When heated, however, the 
zinc coating is removed. 

194. Occurrence of Tin. — Tin is found in nature largely 
in the form of the oxid, Sn0 2 , and, to a less extent, in 
combination with other metals. The oxid is heated in a 
furnace with charcoal, and the molten tin cast into bars. 

195. Tin Salts. — Tin forms two series of salts, stan- 
nous and stannic. In the former, the element is bivalent, 
and in the latter, it is tetravalent. Stannous and stannic 
chlorid, the sulfid, oxid, and hydroxid are among the 
more common tin salts. They are used in the arts in 
various ways as pigments and as mordants in the coloring 
of cloth. Tin forms a number of alloys and is extensively 
used for roofing and for other purposes. Ordinary tin- 
ware is simply iron coated with a layer of tin. 

196. Occurrence of Lead. — Lead occurs principally 
in the form of sulfid (galena). It is also found in combi- 
nation with silver and other metals, and, in the process 
of refining silver, is separated as a by-product. 

197. Oxids of Lead. — There are four oxids of lead ; 
namely, lead monoxid, PbO, lead peroxid, Pb0 2 , lead 
suboxid, Pb 2 0, and lead sesquioxid, Pb 2 3 . The sub- 
oxid, Pb 2 0, is produced when lead is exposed to the air. 
In a pure condition, it is a black powder. Lead oxid, 
PbO, is a yellow powder which, if heated, produces 
litharge, a yellowish red material obtained largely in the 
separation of lead from silver. Lead peroxid, Pb0 2 , is 
an oxidizing agent, and in some respects resembles man- 
ganese dioxid. Red lead or minium, Pb 3 4 , is made by 
heating lead oxid, and is used as a pigment. 

198. Lead Carbonates. — The normal carbonate, 
PbC0 3 , is occasionally found in nature. The basic car- 



144 AGRICULTURAL CHEMISTRY 

bonate, Pb(OH) 3 . 3PbC0 3 , is common white lead so exten- 
sively used as a pigment. It is produced by different 
methods from litharge and other compounds of lead, as 
well as by treatment of the metal itself. 

199. Lead Salts. — Lead nitrate, Pb(N0 3 )2, is produced 
by the action of nitric acid on lead ; and lead sulfate, by 
the action of a sulfate upon a soluble lead salt. Lead 
chlorid, PbCl 2 , is precipitated whenever hydrochloric 
acid or a chlorid is added to a solution containing a lead 
salt. The salts of lead are more insoluble than those of 
many other metals. 

200. Uses of Lead. — Lead is used for making water 
pipes, in the preparation of solder and many alloys, and 
for lining tanks, particularly those in which sulfuric 
acid is stored. Lead is insoluble in most waters, although 
the salts and organic matter in some waters may cause 
enough to dissolve to render the use of lead pipes objec- 
tionable from a sanitary point of view. 

201. Occurrence of Arsenic. — This element occurs in 
the free state to a limited extent, but is usually in combina- 
tion with other elements, as oxygen, iron, and sulfur. 
In some of its properties, arsenic resembles phosphorus, 
and forms similar compounds, although arsenic has 
weaker acid properties than phosphorus. It forms a large 
number of compounds, among which are the arsenates 
and arsenites, which are salts of arsenic and arsenious 
acids. In the presence of a strong base element, arsenic 
deports itself as an acid, while with a strong acid element, 
it exhibits basic properties. Other elements, particularly 
antimony and bismuth, and to a less extent aluminum, 
have this same property of acting both as acid- and 
base-forming elements. Some of the compounds of arsenic 
are extensively used as pigments and insecticides. 



COPPER, ZINC, LEAD, ETC. 145 

202. Paris Green. — Pure Paris green is an aceto- 
arsenite of copper and has the following composition : 
Copper oxid, 31.29 per cent, arsenious oxid, 58.65 per 
cent, acetic acid, 10.06 per cent. Some of the commercial 
grades of Paris green contain an excess of soluble forms of 
arsenic, while others are adulterated with lime and in- 
soluble silicates. The arsenic should be practically 
insoluble and have no injurious effect upon vegetation. 
In case much soluble arsenic is present, the foliage is 
destroyed. Pure Paris green should completely dissolve 
in hydrochloric acid. If silica is a constituent, an 
insoluble residue appears when the material is treated 
with hydrochloric acid. London purple and various 
arsenates and arsenites are occasionally used for insec- 
ticides. London purple contains soluble arsenic. In case 
of accidental poisoning with Paris green, hydroxid of 
iron is usually employed as an antidote. 

203. Occurrence of Mercury. — Mercury is found 
in nature mainly in the form of the sulfid, HgS, commonly 
called vermilion, which, when roasted, yields S0 2 and Hg. 
Mercury is extensively used in the preparation of alloys 
and amalgams. 

204. Compounds of Mercury. — Like copper, tin, and 
many other elements, mercury forms two series of salts, 
the mercurous and mercuric compounds. Mercurous and 
mercuric oxids, Hg 2 and HgO, mercurous and mercuric 
chlorids, HgCl and HgCl 2 , and the nitrates and sulfids 
are among the more important compounds of mercury. 
Mercuric chlorid is employed as an insecticide and 
also as a germicide. It is very poisonous and very 
destructive to all forms of animal and plant life, and 
is frequently used for the treatment of fungus diseases of 
plants. 



146 



AGRICULTURAL CHEMISTRY 



*0 ■ • *400SCt 



fR 



out a paoduc 



«0 J o PHOOuC 



Aftno, 






Fig. 61 



u 



2.na\ot v 



Experiment 35. — Replacement of metals. Place, in separate 
test tubes, (1) 5 cc. of silver nitrate, (2) 5 cc. copper nitrate, and 

(3) 5 cc. of lead nitrate. To the first test tube, add a piece of cop- 
per foil, to the second, a 
small piece of lead, and to 
the third, a piece of zinc. 
After a few minutes, ex- 
amine the contents of the 
various test tubes and ob- 
serve the results. Copper 
has the power of replacing 
silver in solution, lead has 
the power of replacing 

copper, and zinc has the power of replacing lead. 

The more electropositive elements replace those which are less 
electropositive. Observe in these experiments that the copper is 
coated with silver, the lead with copper, and the zinc with lead. 
Write the following reactions which have taken place : 

(1) AgN0 3 + Cu = 

(2) Cu(N0 3 ) 2 + Pb = 

(3) Pb(N0 3 ) 2 + Zn = 

Questions. — (1) Which element is the most positive ? (2) What 
elements can zinc replace ? (3) Why does copper replace silver ? 

(4) Why does lead replace copper ? (5) What does this experiment 
show as to the relative properties of the three elements, copper, 
silver, and lead ? 



PART II 



CHAPTER XXII 

Water Content and Ash of Plants 

205. Water. — There is water in all food materials, 
and in many cases it makes up a large portion of the weight 
of a substance. In vegetables, in milk, and in the juices 
of meat, water is present to such an extent as to be per- 




Fig. 62. — Water oven. 

ceptible to the senses. Substances like flour, meal, and 
starch, which appear to be perfectly dry, are not free 
from water, but contain from 9 to 12 per cent. This 

149 



*5° 



AGRICULTURAL CHEMISTRY 



hydroscopic water, as it is called, is held mechanically by 
the particles of which the material is composed, and the 
amount thus held depends upon the extent of the pre- 
vious drying of the material and the hydroscopic condi- 




Fig. 63. — Analytical balance. 



tion of the air. Inasmuch as there is always some water 
in the air, it necessarily follows that all substances exposed 
to the air must likewise contain some water. 

In order to remove the last traces of water from a 



WATER CONTENT AND ASH OF PLANTS 151 

substance, it is dried either in a water or a hot-air oven 
at a temperature of ioo° C, — the boiling point of water. 
This converts all of the water in the material into steam, 
which is then expelled. A water oven (see Fig. 62) has 
double walls, the space between the walls being partially 
filled with water, which is kept boiling by means of a 
gas burner placed below the oven. The substance to 
be dried is weighed in a suitable dish and then dried in 
the water oven until the weight is reasonably constant, 
the loss of weight being considered water. 

The determination of water in foods, although appar- 
ently simple, is a difficult and troublesome chemical pro- 
cess, because many foods, when heated to ioo° C, suffer 
changes, and give off volatile organic compounds along 
with the water ; or the organic matter may undergo 
change in composition, as oxidation. For determining 
the absolute moisture content of foods, the chemist em- 
ploys a drying bath of different pattern from that shown, 
and the material is dried in a current of 
some neutral gas, as hydrogen, to prevent ^--^N^ 
oxidation of the substance. All dishes A- ;-.._ 'v\ 
in which substances are placed, during V, ^| jS 
analysis, are dried and cooled in desic- Ji~2SJiL__. 
cators out of contact with air, so as to ^S^^^** 1 ^ 
remove all traces of hydroscopic mois- „ _ . 

. . Fig. 64. — Desiccator. 

ture. The weighings are made on ana- 
lytical balances which are scales of extreme accuracy (see 
Fig. 63). Determination of the water is one of the most 
difficult parts of the analysis of plant or animal substances. 
206. Dry Matter. — The dry matter of a material is the 
portion which is left after all of the water has been re- 
moved. Dry matter, as the term implies, is the dry 
material free from all traces of hydroscopic moisture, and 



152 



AGRICULTURAL CHEMISTRY 



"Lt 




the amount is determined by subtracting the per cent of 
water from ioo. For example, if flour contains 12 per 
cent water, there will be 88 per cent of dry matter. The 
amount of dry matter in substances ranges between 
wide limits, as 7 per cent or less in some fruits to 99 per 
cent in granulated sugar. 

Experiment 36. — Determination of water in potato. Carefully 
weigh an aluminum dish (Fig. 65). Cut thin slices from different 
parts of a potato and reduce them to f-inch cubes. 
Weigh in the dish some of these pieces, forming 
a layer not more than two deep. Record the 
weight, place in the dish a small piece 
of paper with your initials, then set the 
dish in the water oven (Fig. 62), and Flp ' 65- 

allow it to remain twenty-four hours, or until the next 
exercise. After drying, weigh again, and from the loss 
of weight calculate the per cent of water in the potato. 
(Weight of potato and dish before drying, minus weight 
of potato and dish after drying, equals 
weight of water lost. Weight of water 
divided by weight of potato taken, mul- 
tiplied by 100, equals the per cent of 
water in the potato.) 

Experiment 37. — Water in flour. 
In the same manner, determine the per 
cent of water in flour, using about 10 
grams of flour, and noting the exact 
weight before and after drying. 

Experiment 38. — Water in milk. 
Weigh a watch glass and place it on 
the water bath (see Fig. 66). Measure 
with a pipette 3 cc. of milk into the 
watch glass. Evaporate to dryness on 
the water bath, completing the process 
in the water oven. When dry, weigh, and from the loss of weight, 
calculate the per cent of solids. Sp. gr. of milk, 1.032. 1 cc. H 2 
= 1 gram. 1 cc. milk = 1.032 grams. If skim milk is used, the 
sp. gr. is 1.035. 





Kg. 66. 



WATER CONTENT AND ASH OF PLANTS 1 53 

Experiment jp. — Water in clover. Weigh an aluminum dish. 
Take three or four large clover plants and cut linely with shears or 
knife. Weigh a portion in the dish ; dry, and weigh again as in 
Experiment 36. Determine the per cent of water in clover. 

Questions. — (1) How did the potato, after drying, compare in 
appearance and volume with the material before drying ? (2) How 
does the percentage amount of water which you have obtained 
compare with the figures given in the tables of analyses ? (3) In 
the determination of water in milk, what was the appearance of the 
milk solids ? (4) What classes of compounds are present in milk 
solids ? (5) How does the amount of water obtained in Experiment 
3 7 compare with the amount given in the tables of analyses ? 
(6) What would be the shrinkage in weight of a barrel of flour if 
2 per cent of moisture were removed, and what would be the in- 
crease in weight if 2 per cent of moisture were absorbed from the 
air ? (7) How does the amount of water obtained in Experiment 39 
compare with that obtained from the other materials ? (8) How 
much water is present in a ton of green clover ? 

207. Plant Ash. — The ash of a plant, or of any ma- 
terial, is that portion which remains after the substance 
is burned at the lowest temperature necessary for com- 
plete combustion. It is sometimes spoken of as the 
mineral or inorganic part, also as the non- volatile part, 
and includes all of the materials, with the exception of 
water and nitrogen, which the plant takes from the soil 
during growth. The term ash as used in chemistry 
differs from the term as ordinarily used in that the chem- 
ical ash is pure ash, free from particles of carbon, and also 
contains elements, as sodium, chlorin, sulfur, and phos- 
phorus, traces of which are volatile at a high tempera- 
ture. Crude ash is obtained by burning a substance 
until all of the carbon is oxidized. 

Experiment 40. — Determination of ash. Weigh to the second 
decimal place in grams a dish given out for this experiment. Then 
weigh into the dish about 2 grams of dry clover or other hay, 



154 



AGRICULTURAL CHEMISTRY 



place in the muffle furnace, and let it remain until there is no charred 
material left. Cool on an asbestos mat. Weigh again and deter- 
mine the per cent of ash from the 
material taken and the weight of 
the ash obtained. Calculate the 
per cent of organic matter. Save 
the ash for future experiments. 
[The 500, 200, and 100 mg. 
weights are to be recorded as 0.5, 
0.2, and 0.1 gram ; the 50, 20, and 
10 mg. weights as 0.05, 0.02, and 
0.01 gram. If one used a 10-gram 
weight, a 500-mg. weight, and a 
20-mg. weight, the weight would 
be written 10.52 grams.] 

208. Form of the Ash Ele- 
ments. — None of the ele- 
ments in the ash of plants 
ever exist there in the ele- 
mentary or free state, as free 

Fig. 67.— Muffle furnace used for sodium Or free silicon, but 
determination of ash. ,1 1 • -u 

they are always m chem- 
ical combination, forming salts, or are combined with 
the elements which con- 
stitute the organic part 
of the plant. The ash 
elements are never pres- 
ent in the form of free 
acids or free bases, 
although, in chemical 
analyses, they are ex- 
pressed as acid or basic 
oxides. Phosphorus, 

Fig. 68. — Weights for balance. 

for example, never ex- 
ists in the plant as free phosphorus or as phosphoric acid, 





WATER CONTENT AND ASH OF PLANTS 1 55 

but either as a phosphate or combined with some of the 
elements which constitute the organic part. 

209. Amount of Ash in Plants. — While the amount 
of ash in plants is fairly constant, it varies with the stage 
of growth, climatic conditions, and nature of the soil. 
In mature agricultural plants, the ash rarely exceeds 
10 per cent of the dry weight of the material. Clover 
grown in different localities is found to contain from 6 to 
8.5 per cent ash; other crops also show limited varia- 
tions. The ash is not evenly distributed throughout all 
parts of a plant ; the leaves, for example, contain more 
than the seed. In the case of corn, the amount of ash 
in different parts is as follows : 

Per cent. 
Mature plant 5.8 

Roots 3.5 

Leaves 8.1 

Stems entire 6.6 

Grain 1.4 

As previously stated, the ash elements of a plant, 
together with the nitrogen and water, represent all of the 
material which is taken from the soil. In 100 parts of 
the dry matter of any crop, from 5 to 10 parts are derived 
from the soil, while 90 to 95 parts are supplied either 
directly or indirectly from atmospheric sources. 

210. Importance of Ash Elements. — Plant ash is 
composed of potassium, sodium, calcium, magnesium, iron, 
phosphorus, sulfur, silicon, and chlorin compounds. 
These, with a few others in small amounts, as aluminum 
and occasionally manganese, boron, etc., are the elements 
which make up the mineral matter of plants. Some 
of the ash elements, as potassium and phosphorus, are 
absolutely necessary for the life of the plant, while others, 



156 AGRICULTURAL CHEMISTRY 

as aluminum and silicon, are, so far as known, unnecessary. 
The essential ash elements are potassium, calcium, 
magnesium, iron, phosphorus, and sulfur. The non- 
essential elements are sodium, silicon, chlorin, and alumi- 
num. Although in some alkali and sea plants, sodium, 
chlorin, and other elements usually considered non- 
essential are needed for growth. 

Chemically considered, the elements found in the ash 
of plants are divided into two classes : 

(1) Metals or base-forming (2) Non-metals or acid-forming 

elements. elements. 

Potassium K Phosphorus P 

Sodium Na Sulfur S 

Calcium Ca Silicon Si 

Magnesium Mg Chlorin CI 

Iron Fe 

Aluminum Al 

To the above list must be added other elements in 
small amounts occasionally found in the ash of plants, 
and also oxygen, which is in chemical combination with 
all of the above elements. 

The essential ash elements are absolutely necessary 
for the normal growth and development of plants. They 
take a direct part in the production of plant tissue. The 
function of each ash element in plant growth has been 
known only, for a comparatively short time. At one time 
it was believed that the ash elements were largely acci- 
dental, that plants in taking up water from the soil could 
not well keep out soluble earthy substances, but sand 
and water culture experiments have demonstrated the 
necessity and the functions of the various ash elements. 

211. Water Culture. — In water culture experiments 
the seed is germinated, and then the roots are suspended 
in water containing small amounts of the different ash 



WATER CONTENT AND ASH OF PLANTS 



157 




elements. The roots are protected from the light, and the 
solution is frequently changed. In case it is desired to 
learn what effect the absence of an element has upon 
the growth and development of the plant, 
all of the elements are supplied in known 
amounts except the one in question, which 
is withheld altogether. The development 
of the plant is observed, and if it reaches 
maturity and produces fertile seeds, it is con- 
cluded that the element withheld is not nec- 
essary to plant growth, while on the other 
hand, if the plant does not develop nor- 
mally, the element withheld is considered 
necessary. By eliminating the ash elements 
in order, conclusions may be drawn as to 
the part which each element takes in plant 
nutrition. After repeated experiments with Fig. 69.— Water 
various modifications, aided by chemical 
and microscopical examinations of the plant, the functions 
of an element are determined. When a plant develops 
under normal conditions, there is a definite part which 
every essential element performs during growth. In fact, 
a plant may be fed, and the effects of the food be ob- 
served as accurately as in the case of the feeding of 
men or animals. 

212. Sand Culture is essentially the same in principle 
as water culture. Pure sand is treated with strong 
acids, washed with distilled water and ignited, and when 
thus properly prepared, furnishes a perfectly sterile 
medium to which is added, as desired, known amonuts 
of the various ash elements in the form of neutral salts. 
The sand serves physically as soil, and the salts supply 
the plant food. 



158 



AGRICULTURAL CHEMISTRY 



Occurrence and Function of Ash Elements 



213. Potassium. — Potassium is one of the most im- 
portant and least variable of all the elements found in 
the ash of plants. It is quite evenly distributed through- 
out the growing plant and generally occurs in the entire 
plant in the largest proportion of any of the essential ash 
elements. It is taken from the soil in the early stages 
of plant growth and is always present to the greatest 
extent in the active and growing parts, as 
in the leaves, where the production of plant 
tissue occurs. Potassium is one of the ele- 
'k: ments most essential for the plant's develop- 
ment. 

The function of potassium is apparently 
to aid in the production and transportation 
of the carbohydrate compounds, as starch 
and sugar, and thus indirectly in the forma- 
tion of all organic matter. In sugar- and 
starch-producing crops, as sugar beets and 
potatoes, potassium takes an important part 
^ in the growth and development. It doubt- 
less has much to do in the way of regulat- 
ing the acidity of the sap by forming organic 
salts, such as potassium bitartrate in grapes. 
At the time of seed formation there is a 
slight retrograde movement of the potash, 
in some cases a small part being returned to 
grown with and the soil. The supply of available potash in 
without potash. ^ e so ^ ^ ias g rea £ influence upon the vigor 

of plant growth. Weak and sickly plants are often 
deficient in potash. Some crops require more for growth 
than do others, and some experience difficulty in obtain- 



WATER CONTENT AND ASH OF PLANTS 1 59 

ing it. Some plants contain such large amounts of potash 
that they are called " potash plants." 

Experiment 41. — Alkalinity of ashes. Weigh 2 grams unleached 
hard wood ashes into a beaker containing 100 cc. H 2 0. Heat over 
a sand bath until it boils; filter. To one half of filtrate, add 10 
drops of cochineal solution; from the burette (see Fig. 38), add 
dilute HC1 (1 cc. acid, 40 cc. H 2 0) until the solution is neutral. 
The alkali in wood ashes is mainly K 2 C0 3 , which is neutralized with 
HC1. Write the reaction. Repeat the experiment, using leached 
ashes. Note number of cubic centimeters HC1 used in each case. 
What do the results indicate ? 

214. Sodium. — This element, which resembles potas- 
sium in its chemical deportment, is not absolutely neces- 
sary for agricultural plants and does not occur in the 
plant ash in such large amounts as potassium. Nearly 
all agricultural plants are brought to maturity without 
its aid, except for the small amount in the seed. Plants 
require so little, if any, that it is not sufficient to take into 
consideration. It is supposed to be an accidental ingre- 
dient, because sodium chlorid is universally present in 
the soil, in water, and occasionally traces of it are in the 
air ; hence plants could not very well exclude it. Some 
alkali plants require and store up large amounts of sodium 
compounds. Unlike potassium, sodium is not so evenly 
distributed through the plant. It has no special move- 
ment, but is found mostly in the lower parts of the plant. 
Seeds contain but little of it, more being in the straw 
and stems. 

215. Calcium. — This element is always present in the 
ash of plants. None of the higher plants can reach 
maturity without a normal supply. Some, like clover, 
beans, peas, and lucern, require so much for their develop- 
ment that they are called " lime plants." Accumula- 



l6o AGRICULTURAL CHEMISTRY 

tions of lime are found in many leafy plants, particularly 
clover, where crystals of calcium oxalate may be observed. 
In leaves, it appears to have the special function of 
aiding in the construction of the cell walls. No new plant 
cells can be produced without the aid of calcium. 

From the culture experiments of various investigators, 
calcium appears to take a prominent part in the produc- 
tion of new tissue. Whenever it is withheld, the growth 
of the plant is restricted. Some plants, after their growth 
has been checked by withholding calcium, will show 
increased vigor within a few hours after it is supplied. 
Calcium is assimilated in the early stages of plant develop- 
ment. In wheat, for example, 80 per cent is assimilated 
before the plant heads out. Calcium assists in imparting 
hardiness to crops. It does not accumulate in the seeds 
to such an extent as do other elements. Only about 
one tenth of the total amount removed in grain crops is 
in the seeds, the remaining nine tenths being present in 
the straw. Crops grown on lime soils are usually well 
nourished, and are more capable of withstanding unfa- 
vorable climatic conditions, as drought and early frosts, 
than are crops not so liberally supplied with lime. 

Experiment 42. — Lime, CaO, in plant ash. Transfer the ash 
from Experiment 40 to a beaker containing 5 cc. HC1 and 50 cc. 
H 2 ; heat ten minutes, filter, and divide into two portions. Save 
portion for Experiment 44. Make one portion neutral with am- 
monia, NH4OH. Add 5 cc. NH4CI solution. To the solution, add 
5 cc. ammonium oxalate, (NH 4 )2C 2 4 ; note the precipitate which 
is calcium oxalate, CaC2C>4. 

Into a separate test tube put 0.1 gram CaCl2, add 5 cc. H 2 and 
a little HC1 until acid ; then nearly neutralize with NH 4 OH and 
add NH4CI and (NH 4 ) 2 C20 4 . Compare this precipitate with that 
from the clover ash. Observe, in this second test, that you have 
taken a pure calcium salt, and that the same precipitate was given 



WATER CONTENT AND ASH OF PLANTS l6l 

as by the plant ash. Write the following reactions which have 
taken place : CaC 2 4 + Heat = ? CaC0 3 + HC1 = ? CaCl 2 + 
(NH 4 ) 2 C 2 4 = ? 

216. Magnesium is also an essential element. It 
occurs in all plants and farm crops in somewhat smaller 
amounts than calcium, but in the seeds of grains it is 
stored up three times more liberally. Magnesium is 
assimilated more slowly than calcium ; in fact, it is assimi- 
lated, as a rule, more slowly than any other ash element. 
The plant does not require magnesium until the approach 
of seed formation, although a small amount is necessary 
for perfect leaf action as it enters into the chemical compo- 
sition of the chlorophyll. When plants are grown with an 
incomplete supply of magnesium, the seeds are frequently 
sterile. In culture experiments, the absence of magne- 
sium is not observed so much in the first stages of growth 
as near the time of seed formation, when its absence is 
followed by restricted development. 

217. Aluminum is found in the ash of many plants, as 
wheat, peas, beans, and rice, although it occurs in very 
small amounts and, so far as known, is not essential for 
plant growth. Most soils contain traces of soluble sili- 
cates of aluminum, and hence plants cannot well be free 
from this element. 

218. Iron is necessary for plant growth. It occurs 
in about the smallest amount of any of the ash elements, 
but is always present in pjants. When plants are unable 
to obtain their requisite supply of iron, the production 
of chlorophyll does not take place and they fail to develop 
a normal green color. 

The function of the iron is to assist in the formation of 
chlorophyll, the coloring matter of plants. It is not known 
whether iron enters into the chemical composition of 

M 



162 



AGRICULTURAL CHEMISTRY 



the chlorophyll, or is simply organically associated 

with it. 

219. Phosphorus, in the form of phosphates, is found 

in all parts of plants. It is one of the essential elements 

for plant growth. Its function is to aid in the produc- 
tion and transportation of the proteid 
bodies. The phosphorus and nitrogen 
compounds are closely associated in the 
work of producing proteids, which can 
take place only in the plant cells. The 
proteid compounds produced in the 
leaves of plants are finally transported 
to the seed. Many proteids which are 
insoluble in water are soluble in the pres- 
ence of phosphate compounds. The phos- 
phates are essential in the early stages of 
the plant's development. In the case of 
wheat, 80 per cent is assimilated in the 
first fifty days, and in other crops, the 
assimilation is equally rapid. The phos- 
phates accumulate to a greater extent in 
the seeds of grains than in the leaves and 
stems. From 60 to 75 per cent of the 
total phosphates are removed in the 
seeds. The loss of phosphates from 
one of the reasons why soils decline in 




Fig. 71. — Plants 
grown with and 
without phosphoric 
acid. 



the farm is 
fertility. 



Experiment 43. — Phosphoric acid in seeds. Crush 25 kernels 
of wheat in a mortar. Place the crushed wheat in a small Hessian 
crucible and ignite ; when cool, transfer the charred mass to a small 
beaker. Add 10 cc. concentrated HN0 3 and 50 cc. H 2 0, and boil 
ten minutes. Break the charred particles with a stirring rod 
during the boiling. If the beaker shows signs of becoming dry, add 



WATER CONTENT AND ASH OF PLANTS 1 63 

a little hot water. Filter. To half the filtrate add 3 cc. ammo- 
nium molybdate. The yellow precipitate is ammonium phospho- 
molybdate. See Experiments 17 and 18. 

220. Sulfur also is an essential element of plant and 
animal bodies, but occurs in plant tissue in comparatively 
small amount. It enters into the composition of albu- 
min and other proteids. Sulfur is used by plants only 
in the form of sulfates. It takes a part in plant life, 
as there must be a supply of sulfur for the proteid com- 
pounds which always contain this element in chemical 
combination. Culture experiments show that in its 
absence no growth results. As sulfur forms a part of the 
volatile products when a plant is burned, that present in 
the ash represents only a portion of the sulfur taken by 
the plant from the soil. 

Experiment 44. — Sulfur as sulfates in plant ash. To the second 
portion of the filtrate from Experiment 42 add 2 cc. barium chlorid, 
(BaCl 2 ), observe the result, and write the reaction, assuming S0 3 to 
be in the form of K 2 S0 4 . In a second test tube, add a few crystals 
of Na 2 S04 or K2SO4 to 10 cc. H 2 containing a few drops HC1. 
When dissolved add BaCl 2 and compare with precipitate obtained 
in first part of experiment. 

221. Chlorin is not an essential ash element. It accu- 
mulates mainly in the lower part of the plant, and its 
presence appears to be accidental, it having no decided 
functions to perform. The statements made about 
sodium, its occurrence, distribution, and importance 
apply also to chlorin, with which it is combined, forming 
sodium chlorid. 

222. Silicon occurs in all plants. It is found in largest 
amounts in the dense and older parts, as the stalk and 
straw, where there is less activity. In some of the lower 
plants, as diatoms, there is so much silica that when the 



164 AGRICULTURAL CHEMISTRY 

organic matter is removed by burning, a skeleton of silica 
is left. It was formerly supposed that silica gave the 
stems of grains and grasses their stiffness. Perfect wheat, 
however, with normal strength of straw has been grown 
in the absence of silica, except for the small amount 
originally present in the seed. Lawes and Gilbert have 
shown that the lack of silica is not the cause of grain 
lodging. Some authorities claim that silica takes a part 
in plant economy and is necessary in seed formation. 
Whatever its function, it is not an important element as 
plant food, and there is always an abundance in the soil 
for crop purposes. 

In the living plant, the mineral elements are not in the 
same form or combination as in the plant ash. During 
growth, many of the ash elements are combined with the 
organic compounds, for example phosphorus, which forms 
phosphorized proteids and fats. The ash forms a part 
of the plant tissue. When the plant is burned, the organic 
compounds are volatilized, while the ash elements, which 
are non- volatile, are left. The essential ash elements 
are absolutely necessary as food for the growth and 
development of all crops, and plant growth is frequently 
arrested because of the lack of a sufficient supply for 
purposes of nutrition. The food requirements of indi- 
vidual farm crops are discussed in " Soils and Fertilizers." 



WATER CONTENT AND ASH OF PLANTS 



165 



Summary Table. 
Plant ash elements. 



+ 1 



Function. 



Assists in formation 
of starch, carbohy- 
drates, and in plant 
growth in general, 
and makes plants 
vigorous 

No function 

Assists in formation 
of plant cells, and 
makes plants hardy 

Aids in seed formation 

Aids in chlorophyll for- 
mation 

No function 

No function 



Leaf action and for- 
mation and move- 
ment of proteids 
Production of proteids 
No apparent function 
No apparent function 

Problem 1. — How many pounds of potash are removed from an 
acre of soil yielding 150 bushels of potatoes ? 

The potatoes weigh 60 pounds per bushel. 150 X 60 = 9000 
pounds, total yield of potatoes. The potatoes contain 24 per cent 
dry matter (see Table). This dry matter contains 3.8 per cent 
ash. Hence 2160 pounds dry matter contain (216 X 0.038 = 82.08) 
82.08 pounds ash. 60 per cent of this ash is potash ; or (82.08 X 



Metals. 


cd 




Occurrence. 




3 


CxJ V 

^ c 








Pn 







Potassium 


K 2 


+ 


Mainly in the ac- 
tive growing 
parts of plant 
leaves and 
stems 


Sodium 


Na 2 


— 


Stems and roots 


Calcium 


CaO 


+ 


Leaves and stems 


Magnesium 


MgO 


+ 


Seeds and leaves 


Iron 


Fe 2 3 


+ 


Leaves and stems 


Aluminum 


A1 2 3 


- 


Lower parts of 
plants 


Manganese 


Mn 2 3 




Lower parts of 
plants 


Non-metals. 








Phosphorus 


P2O5 


+ 


Seeds 


Sulfur 


S0 3 


+ 




Silicon 


Si0 2 


— 


Stems and leaves 


Chlorin 




— 


Lower parts 



1 66 AGRICULTURAL CHEMISTRY 

0.60) 49.25 pounds are potash. Therefore, 150 bushels of potatoes 
remove from the soil 49.25 pounds of potash. In the same way, the 
amount of each separate element removed from the soil may be 
calculated. 

Problem 2. — Calculate the pounds of total ash, K 2 0, CaO, MgO, 
and P2O5, removed in 25 bushels of wheat. 

Problem 3. — Calculate the same ingredients removed in 1500 
pounds of wheat straw. Compare these with the corresponding 
elements removed in the grain (Problem 2). 

Problem 4. — Calculate the CaO, MgO, K 2 0, and P 2 5 removed 
in 50 bushels of oats weighing 32 pounds per bushel. 

Problem 5. — Calculate the same for 40 bushels of barley weigh- 
ing 48 pounds per bushel. In what respects does the mineral food 
of barley differ from the mineral food of wheat ? 

Problem 6. — How much P2O5 is removed in 15 bushels of flax ? 



WATER CONTENT AND ASH OF PLANTS 



167 



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CHAPTER XXIII 
The Non-nitrogenous Organic Compounds of Plants 

223. Organic Matter. — The organic matter of a plant 
or material of any kind is that portion which can be 
converted into volatile or gaseous products ; it is the 
combustible part, and is simply a mechanical mixture 
of the various organic compounds, as starch, sugar, and 
fat, of which the material is composed. The term organic 
compounds was originally applied to those bodies which 
it was believed could be produced only as the result of 
life processes, but it is no longer used in that sense because 
many of the organic compounds are now produced in 
the laboratory by synthetic methods. The organic 
matter of a substance is obtained by subtracting the ash 
from the dry matter. The dry matter of wheat, for 
example, contains 2.10 per cent ash and 97.90 per cent 
organic matter. The organic matter of plant and animal 
bodies includes a number of classes and types of com- 
pounds. 

224. Non-nitrogenous and Nitrogenous Organic Com- 
pounds. — For purposes of study, the organic compounds 
of animal and plant bodies are divided into two large 
classes: (1) nitrogenous, and (2) non-nitrogenous. This 
division is made on the presence or absence of the element 
nitrogen. The nitrogenous or nitrogen-containing com- 
pounds are those in which the element nitrogen is in 
combination with carbon, hydrogen, oxygen, and small 

168 



ORGANIC COMPOUNDS OF PLANTS 



169 



amounts of other elements, while the non -nitrogenous 
compounds are those which contain no nitrogen, but are 
composed of carbon, hydrogen, and oxygen. Starch, 
sugar, and fat are types of non-nitrogenous compounds, 
while albumin, casein, and fibrin are types of the nitrog- 
enous. 

225. Classification of Non-nitrogenous Compounds. — 
There are six large divisions of the non-nitrogenous com- 
pounds : (1) carbohydrates, (2) pectose substances, 
(3) fats, (4) organic acids, (5) volatile or essential oils, 
and (6) mixed compounds. Each division is, in turn, 
divided into various subdivisions and groups : 



Carbohydrates, 

Cellulose, 

Starch, 

Sugar, 

Pentosans, 

Gums. 

Pectose substances (jellies). 

(i. Olein, 
2. Stearin, 
3. Palmitin, etc. 

11. Tartaric, 
2. Oxalic, 
3. Malic, etc. 
Volatile or essential oils. 



Organic non-nitrogenous 
compounds 



6. Mixed compounds. 



Carbohydrates 



226. General Characteristics. — Carbohydrates, the first 
subdivision of the non-nitrogenous compounds, include 
the starches, sugars, gums, cellulose and pentosan bodies. 
They form the largest group of the organic compounds 
in plants, and in many plants and food materials are 
present largely as starch. The carbohydrates occur in 



170 AGRICULTURAL CHEMISTRY 

plants in three physical forms : (1) as the framework of 
the plant cells, as cellulose, (2) in solution in the plant 
sap, as sugar, and (3) deposited as solid substances within 
the plant cells, like starch. In coarse fodders, as hay, 
they are largely in the form of cellulose and pentosan bodies. 
While the various carbohydrates differ chemically and 
physically, they all possess a few common characteristics : 
(1) they are all neutral bodies, and (2) they all contain 
twice as many hydrogen as oxygen atoms in their mole- 
cules. The H and O are present in the same proportion 
as found in water, viz., 2 atoms of H and 1 of O. In 
starch, C 6 Hi O 5 , the H and O would form 5 H 2 0. 

Cellulose 

227. Occurrence. — Cellulose is found most abundantly 
in the stems, roots and leaves of plants, particularly at 

maturity. It is the structural basis 
of the vegetable world, and forms 
the framework of every plant cell. 
In some plants it is the most 
abundant material present ; in hay 
and coarse fodders it makes up 
from 30 to 40 per cent of the dry 
Fig. 72.— Cell structure of matter. Crops like cotton, flax, 
plant tissue. an( j ^ em ^ con t a in large amounts, 

and are cultivated mainly for the cellulose which they 
yield. 

228. Physical Properties. — Pure cellulose is a colorless 
insoluble material, differing in texture according to its 
source. In hemp, it is flexible and tenacious, while in 
wood it is hard and compact ; in the pith of the elder, it is 
elastic, in the potato, porous, and in germinating seeds, 
loose and spongy. Cotton and filter paper are examples 




ORGANIC COMPOUNDS OF PLANTS 



171 




Fig. 73. — Flax fiDcr. 



of nearly pure cellulose. The proportion and properties 
of cellulose in a food influence its digestibility. Some foods 
are less valuable because of the 
tenacious character of the cellu- 
lose, which prevents the cells from 
undergoing disintegration and 
digestion. 

229. Chemical Properties. — 
Cellulose is composed of carbon, 
hydrogen, and oxygen. Its for- 
mula is C 6 Hi O 5 . Cellulose from 
one source may have a different 
multiple of C 6 Hi O5 than that 
from another source. In young 
and growing plants, the cellulose is 
in a hydrated condition ; that is, water is chemically 
united with the cellulose molecule, as (C 6 Hi O 5 . H 2 0) n . 
Hydrated cellulose is more readily acted upon by chemicals 
than are other forms. As the plant develops, the cellulose 
is gradually dehydrated, and this is one reason why 
cellulose, at different stages of growth, has different food 
value. Lignocellulose is found in wood and many mature 
plants. It contains a larger per cent of carbon than 
does cellulose. 

230. Function and Value. — In the plant, the function 
of cellulose is to form the structural part of the cell walls. 
It constitutes the main portion of the walls of every plant 
cell. In seeds, it is a reserve food material for the young 
plant. Commercially, cellulose is employed for making 
paper, cloth, guncotton, and other explosives, and is 
extensively used in the arts. 

231. Food Value. — The food value of cellulose depends 
upon its degree of hydration. Hydrated cellulose, when 



172 AGRICULTURAL CHEMISTRY 

digested, has practically the same food value as starch. 
Lignocellulose is indigestible, and has no food value. 
Indirectly, a minimum amount of cellulose imparts 
mechanical value to a food by acting as an absorbent for 
concentrated waste products. When crops are cut and 
cured while some of the cellulose is in a hydrated condi- 
tion and but little has passed into the ligno form, the 
cellulose is valuable as food. 

232. Amount of Cellulose in Plants. — Cellulose is 
found more abundantly in the stems and leaves of plants 
than in the seeds. In the straw of wheat, oats, rye, and 
barley, it makes up from 35 to 45 per cent of the dry 
material. It also constitutes a large portion of the roots 
of plants. In seeds, the amount of cellulose is small, and 
usually ranges from 2 to 5 per cent, while in wood, the 
range is from 50 to 80 per cent. In tables of analyses, 
the cellulose is usually included with other bodies under 
the head of crude fiber. 

233. Crude Fiber. — Crude fiber includes the cellulose, 
lignin, and other materials which make up the framework 
of vegetable substances. In vegetable foods, as flour and 
the cereal products, the amount of crude fiber is small 
compared with that in many other plant bodies. Crude 
fiber and cellulose are not identical terms. In the chem- 
ical analysis of plants, the crude fiber is determined by 
first digesting the material in dilute sulfuric acid to 
dissolve all that is soluble, as sugar, hydrolyzed starch, 
some of the proteids and related bodies. The substance 
is then digested with dilute sodium hydroxid to remove 
all compounds which have failed to dissolve in the acid. 
Crude fiber and insoluble mineral matter are about the 
only substances which are insoluble in the dilute acid and 
alkali, hence the fiber is obtained by dissolving all other 



ORGANIC COMPOUNDS OF PLANTS 1 73 

compounds and deducting the insoluble mineral matter 
left. For the determination of cellulose more exact 
methods have been devised. The crude fiber determina- 
tion, however, is valuable because it shows the amount 
of fibrous material contained in plants. 

Experiment 45. — Preparation of cellulose. Place in a beaker 
about 1 gram of ground straw or hay ; add 200 cc. of water, and 20 
drops of H2SO4. Boil on the sand bath twenty minutes, and after 
the material settles, pour off the liquid, then add 100 cc. water, 
and wash thoroughly by decantation. Add 200 cc. water and 4 cc. 
NaOH solution, boil twenty minutes, and wash the fibrous material 
as before. Place some of the crude fiber in a test tube, add 5 cc. 
HC1, 10 cc. H 2 0, and a crystal of KC10 3 ; heat, and then wash the 
cellulose product. 

Questions. — (1) What element was liberated by the action of 
HC1 upon the KCIO3 ? (2) What effect did this element have in the 
bleaching and purification of the crude fiber? (3) In what other 
experiment has this element been used as a bleaching reagent ? 

(4) When examined with a lens, how did the cellulose appear ? 

(5) Is cellulose soluble in dilute acids ? (6) Why were the dilute 
acid and alkali solutions used in this experiment ? (7) What be- 
comes of the ash or mineral matter in the material used in this ex- 
periment ? (8) What does this experiment show in regard to the 
properties of cellulose ? 

Starch 

234. Occurrence. — Starch is found most abundantly in 
the seeds, roots, and tubers of plants, being stored up in 
those parts which are concerned with new growth. Dur- 
ing growth, starch is produced in the leaves of all green 
plants ; at maturity, it is stored in the seed or tuber. 
It is present in the plant cells as granules which have 
regular organized forms. 

235. Physical Properties. — The starch granules from 
a given cereal are always constant in form and physical 



174 



AGRICULTURAL CHEMISTRY 



properties. Each grain is composed of overlapping layers 
which can be observed under the microscope. The walls 
of the layers are composed of a material called " starch 
cellulose " ; between the walls is the pure starch known 
as granulose. All starch grains have a somewhat similar 
general structure. Starch is insoluble in cold water be- 
cause the walls of starch cellulose prevent the water from 
dissolving the pure starch. In hot water some of the 
granulose is dissolved and a paste is formed. Pure dry 
starch is tasteless and odorless. Starch is exceedingly 
hydroscopic, and commercial starch always contains from 
10 to 12 per cent, or more, of water. A food which 
contains a large amount of starch will vary in moisture 
content and weight according to the hydroscopicity of the 
air. The starch grains obtained from different cereals 
and food products vary in form according to the source 

from which they are 
obtained. Wheat 
starch is circular in 
outline, and has a 
slightly concave 
center. There are 
but few markings or 
rings (see Fig. 74). 
The granules vary in 
size from 0.05 to 0.01 
millimeter in diame- 
ter. Cornstarch is 
somewhat smaller 
(0.02 to 0.03 millimeter), more angular than wheat starch, 
and has a star-shaped center or helum (see Fig. 75). Oat 
starch is composed of a number of small segments forming 
a compound grain, or mass, each segment in itself a com- 




Fig. 74. — Wheat starch. 



ORGANIC COMPOUNDS OF PLANTS 



175 



plete structure. Barley and rye starch grains are some- 
what similar to wheat. In some vegetables, as the parsnip, 
the starch grains are minute. 

236. Chemical Properties. — Starch is composed of 
carbon, 44.44 per cent; hydrogen, 6.17 per cent; and 
oxygen, 49.39 per 
cent. Its formula 
is (C 6 H 10 O 5 )n. The 
value of n has been 
variously estimated 
from 2 to 200. The 
different starch 
grains, as of wheat, 
corn, and oats, are 
all composed of the 
same elements, C, H, 
and O, and differ in 
form because these 
elements are put to- 
gether in a different way in each. When acted upon by 
heat, as in the popping of corn, the starch grains are 
ruptured . At a temperature above 1 2 o ° C . , starch gradually 
is changed to dextrin. In the presence of water and dilute 
acids, starch gradually undergoes hydration ; that is, water 
is chemically added to the molecule. By the joint action 
of heat, ferments, and various chemicals, starch is con- 
verted into a number of products, as soluble starch and 
dextrose. In the presence of iodin, starch is colored 
blue, different kinds of starch giving different shades and 
tints. The nature and mechanical form of the starch 
granules in a food determine, to a slight extent, its rapidity 
and ease of digestion. Some starches are more easily 
digested than others, and all undergo important chemical 




Cornstarch. 



176 AGRICULTURAL CHEMISTRY 

and physical changes in their cooking and preparation as 
food. Since starch makes up such a large portion of 
many human and animal foods, its composition, properties, 
and food value are of prime importance. 

237. Function and Value. — In the seed, starch is a 
reserve form of food for the use of the young plant before 
it is able to obtain its own food ; in roots and tubers also, 
it is stored up for that purpose. Many crops, as pota- 
toes, corn, and sago, contain so much starch that they 
are often cultivated for starch-making purposes. Starch 
is obtained mechanically from potatoes by first pulping 
to break the cells, and then washing the pulped mass 
with water from which the starch slowly settles. In the 
arts, starch is used in many ways. As a food, it is used 
mainly in its original form associated with the other or- 
ganic compounds with which it is found in plants. 

238. Food Value of Starch. — Starch is a valuable 
nutrient, and when digested, produces heat and energy. 
When burned in the bomb calorimeter 1 pound of digestible 
starch produces i860 calories. A calorie is the unit 
employed for measuring heat, and is the amount of heat 
required to raise 1 kilo of water i° C, or approximately 
1 pound of water 4 F. One gram of starch yields 4.2 
calories. Pure starch alone is incapable of sustaining life, 
because it contains no combined nitrogen, and does not 
supply any material for repairing the tissues of the body 
or for the construction of new nitrogenous tissue. When 
associated with nitrogenous compounds, starch can be 
used by the body for the production of fat as well as for 
the production of heat and energy. 

239. Amount of Starch in Plants. — In grains, the 
amount of pure starch ranges from 50 to 75 per cent of 
the dry weight of the material ; in hay and forage crops, 



ORGANIC COMPOUNDS OF PLANTS 



177 



it is small, usually less than 2 per cent. The amount of 
pure starch in some of the cereals and farm crops is approx- 
imately as follows : 

Pure starch. 
Per cent. 

Wheat 68 

Wheat flour 72 

Oats 55 

Corn 75 

Rice 78 

Potatoes 80 

Wheat bran 8 

Straw less than 1 

Hay 1 to 3 

Experiment 46. — Preparation of potato starch. Reduce one or 
two clean potatoes to pulp on the grater. Tie the pulp in a clean 
cloth and squeeze into a large cylinder filled with water, occasion- 
ally dipping the bag into the water. Allow the cylinder to stand 





Fig. 76. — Obtaining starch from potato. 

for twenty minutes, or until the starch has all settled ; pour off the 
water. If the starch is not clean, wash by adding more water, and 
allow it to settle again ; then pour off the water. Leave the cylin- 
der in the desk until the starch is dry. Save this starch for the 
following tests: Tests for starch. Place 0.5 gram of starch in a 

N 



178 AGRICULTURAL CHEMISTRY 

test tube, about one half full of water. Shake the test tube, boil, 
and filter ; then to this filtrate add a few drops of iodin. Treat a 
second portion of starch with cold water and then add iodin. 

Questions. — (1) What was the difference in the action of hot and 
cold water upon starch? (2) How did this difference show itself 
in the tests ? (3) Why in the one test tube were there a blue mass 
and a clear liquid, and in the other opposite results ? 

240. Dextrin is a carbohydrate which has the same 
general formula as starch, from which it differs in struc- 
tural composition. Dextrin is produced from starch by 
the action of heat. When this change takes place, 
nothing is added to or taken from the starch molecule. 
The three elements, C, H, and O, are simply rearranged 
in the new molecule. Dextrin is not found naturally 
in food products to any appreciable extent, but is present 
in starch-containing foods which have been subjected 
to the action of heat. The brown crust of bread is com- 
posed mainly of dextrin. Dextrin is soluble in water, 
and is more readily digested than starch, but it has the 
same general fuel and energy -producing value. 

Experiment 47. — Preparation of dextrin. Place about 2 grams 
of flour in a porcelain dish ; heat cautiously on a sand bath for five 
minutes, constantly stirring, so that it will not burn. When cool, 
add three times its bulk of water and heat nearly to boiling ; ob- 
serve the appearance of the solution ; then filter. The filtrate con- 
tains dextrin. To a portion, add twice its bulk of alcohol ; the 
dextrin is precipitated. To another portion, add a few drops of 
iodin solution ; blue color indicates soluble but unaltered starch. 

Questions. — (1) What agent was employed to change the starch 
to dextrin ? (2) How does dextrin differ from starch in solubility ? 
(3) Is dextrin soluble in alcohol ? (4) In what ways does dextrin 
differ from starch ? 

241. Structural Formulas. — Cellulose, starch, dextrin, 
and inulin have the same general formula (C 6 Hi O 5 )n, but 
all differ both in physical and chemical properties. This 



ORGANIC COMPOUNDS OF PLANTS 1 79 

is because the elements, C, H, and O, are put together in 
different ways in the three compounds. For example, a 
pile of bricks may be put together to form one structure, 
and again in different ways to form other structures, 
while in each structure there are the same number and 
kinds of bricks. So in the molecules of starch, dextrin, 
inulin, and cellulose, there are the same number and kinds 
of atoms, but in each they are combined in a different 
way. In the study of the composition of plants, organic 
compounds are frequently met with which have the same 
general composition, but different chemical and physical 
properties. Whenever two compounds have the same gen- 
eral formula and percentage composition, but different 
chemical and physical properties, the difference is said 
to be one of structural composition. 

Sugar 

242. Classification of Sugars. — As commonly used, 
the term sugar is applied to the product obtained from 
sugar-cane or sugar-beets. As used in chemistry, it 
includes a large class of compounds of which maple-, 
cane-, and beet-sugar are examples of only one division. 
The two main classes of sugars present in plant bodies are 
sucrose and dextrose ; occasionally, other sugars are found. 

The sucrose group includes cane-, beet-, maple-, milk-, 
and malt-sugar. These sugars have the general formula 
C12H22O11, and are characterized by the molecule contain- 
ing 12 atoms of carbon. The dextrose group includes 
glucose, levulose, galactose, and all sugars having the 
general formula C 6 Hi 2 6 . This group is characterized by 
the molecule containing 6 atoms of carbon. The term 
monosaccharide is applied to the dextrose group, and 
disaccharide to the sucrose group. 



l8o AGRICULTURAL CHEMISTRY 

243. Occurrence of Sucrose. — Sucrose is found in 
plants in largest amounts of any of the sugars. Juices 
from the sugar-cane and sugar-beet contain from 12 to 18 
per cent. It is also, in small amounts, in seeds and cereal 
products. From 1.5 to 2 per cent is found in sweet corn 
and about 0.50 per cent in wheat flour. In some fruits, 
as apples, sucrose is present to the extent of 5 per cent or 
more. 

244. Physical and Chemical Properties of Sucrose. — 
The chemical and physical properties of sucrose obtained 
from sugar-cane or sugar-beets are alike in all respects. 
When the two sugars have been subjected to the same 
degree of refining, they are identical. When examined 

under the microscope, sucrose is in the form 
of regular crystals, as shown in the illustration 
(see Fig. 77). Above 160 C. sucrose crystals 
Fig. 77 • — Su- melt, and when cool form a colorless, glassy 
arose ays a . mass _ ^ concentrated solution boils at a 
little above ioo° C. At 160 C. a brown product known 
as barley sugar is formed. At 200 C. sucrose is decom- 
posed, and gases, as carbon monoxid, carbon dioxid, and 
methane, are given off. In concentrated solutions, a 
temperature of ioo° C. causes an inversion ; that is, the 
sucrose molecule is split up and two new sugars are formed ; 
namely, dextrose and levulose. Hence, in the refining 
of sugar, the concentration must be carried on in vacuum 
pans. In the presence of all acids, even dilute organic 
acids, hydrolysis or inversion of sucrose takes place. 

245. Milk Sugar (lactose) is found in cow's milk to 
the extent of 4.5 to 5 per cent, and is present in the milk 
of all mammals. It has the same general composition as 
sucrose, but a different structural composition. 

246. Maltose is a sugar produced in the malting of 




ORGANIC COMPOUNDS OF PLANTS l8l 

barley and other grains by the action of ferments upon 
starch, the reaction being 

2 C 6 H 10 O 5 + H 2 = C 12 H 22 0n. 

Maltose is not found to any extent in plant bodies, but is 
present in prepared foods which have undergone the malt- 
ing process. 

247. Inversion of Sucrose. — When sucrose is acted 
upon by heat and dilute acids, as well as other chemicals, 
inversion takes place. One molecule of water is chemi- 
cally united to one molecule of sucrose which splits up 
and forms the two sugars, levulose and dextrose. 

Sucrose. Levulose. Dextrose. 

Ci 2 H 22 0n + H 2 = CeHi 2 06 + C 6 Hi 2 06. 

This process takes place in the ripening of fruits and in 
the curing of many fodders, as well as in the cooking and 
preparation of human foods. 

Experiment 48. — Inversion of cane-sugar. Place 2 grams 
sugar, 30 cc. H 2 0, and 2 cc. H2SO4 in an evaporator. Heat fifteen 
minutes on a sand bath, replacing the water lost by evaporation. 
Neutralize with CaC0 3 and filter, adding more water if necessary 
for filtration. Test 5 cc. of the filtrate with an alkaline solution of 
copper sulfate (Fehling's solution) as directed in Experiment 34. 
Take o. 1 gram of sugar, dissolve in 10 cc. cold water, add 2 cc. 
alkaline copper sulfate solution, and heat cautiously for about a min- 
ute. Cane-sugar, unless inverted, gives no reaction with copper sul- 
fate solution. Compare this result with the first test. Observe that 
in the first test the same precipitate is obtained as in Experiment 34. 

Questions. — (1) What is meant by inversion of cane-sugar? 

(2) Why was hot sulfuric acid used ? Write the reaction. 

(3) Why was CaC0 3 used ? (4) What becomes of the calcium salt 
when the solution is filtered ? (5) What was the result when the 
nitrate was heated with alkaline copper sulfate solution (Fehling's 
solution) ? (6) Did the sucrose, when tested, give any reaction 
with this reagent ? (7) Under what condition in nature does this 
process of inversion take place ? (8) What are invert sugars ? 



1 82 AGRICULTURAL CHEMISTRY 

248. Refining Sugar. — At the present time, the 
larger portion of commercial sugar is obtained from sugar- 
beets. In the diffusion process of manufacture, the beets, 
after cleaning and slicing, are passed into large tanks, 
where they are subjected to water under pressure which 
removes the sugar by liquid diffusion. The impurities 
associated with the sucrose are precipitated with lime 
water, Ca(OH) 2 , the excess of lime being removed by 
carbon dioxid gas which converts the calcium hydroxid 
into insoluble calcium carbonate. For the purpose of 
producing the pure lime and the carbon dioxid gas, lime- 
stone is burned in specially constructed kilns at the sugar 
factory. After removal of the impurities and the lime, 
the solution containing the sugar is concentrated in a 
large vacuum pan and allowed to crystallize ; the crys- 
tals are then washed in centrifugal washing machines 
and granulated. Commercial sugar is ordinarily about 
99 per cent pure sucrose. 

249. Occurrence of Dextrose. — Dextrose occurs widely 
distributed in nature. It is found in small amounts in 
the sap of saccharine plants, in seeds, ripe fruit, honey, 
animal tissues, and in all food products in which the 
sucrose has undergone inversion. 

250. Chemical and Physical Properties. — Dextrose is a 
solid, white substance which gives off water from its mole- 
cule when heated to 170 C. At 200 C, volatile gases 
and acid products are formed. Acids and alkalies act 
upon dextrose and produce a large number of compounds. 
Dextrose can undergo a number of different kinds of 
fermentation, alcohol, succinic acid, lactic acid, and 
glycerol being some of the products formed. Whenever 
foods which contain dextrose are exposed to favorable 
conditions, fermentation takes place. Dextrose is pro- 



ORGANIC COMPOUNDS OF PLANTS 1 83 

duced commercially by the action of dilute acids upon 
starch. The acid causes a molecule of water to unite 
chemically with a molecule of starch. 

C6H10O5 + H 2 = C 6 Hi 2 6 . 

The thick syrup formed after the acid is neutralized is 
called glucose syrup. If a solid mass is produced, it is 
called grape sugar. 

Experiment 4g. — Preparation of glucose. Add 20 drops H2SO4 
to about 70 cc. water in an evaporator. Heat on the sand bath 
until the boiling point is reached. Then add 2 grams of pulverized 
starch. Observe the appearance of the starch immediately after 
adding. Heat twenty-five minutes, stirring occasionally, and re- 
placing the water should too much evaporate. Add CaC0 3 to 
neutralize the H2SO4 ; when neutral to test paper, filter, washing 
the contents of the filter with 25 cc. of water. Take a few drops of 
the filtrate and test with iodin for starch. Then evaporate the rest 
of the filtrate to about 20 cc. and observe its appearance. 

Tests for glucose. Place about 3 cc. of glucose solution in a test 
tube, add 3 cc. alkaline solution of copper sulfate (Fehling's solu- 
tion ; see Experiment 34), and heat. Dissolve .1 gram glucose in 
5 cc. water ; add 3 cc. Fehling's solution. Heat, and compare with 
the first test. 

Questions. — (1) Why was sulfuric acid used in this experiment? 
(2) What chemical change did the starch undergo ? Write the re- 
action. (3) Why was CaC0 3 used ? Write the reaction. (4) Was 
any reaction obtained with iodin for starch ? (5) What was the 
result when the glucose solution was added to the hot alkaline 
solution of copper sulfate ? (6) How did this precipitate compare 
with that obtained when glucose from the shelf bottle was used ? 

251. Levulose, commonly called fruit sugar, is formed 
along with dextrose whenever sucrose undergoes inver- 
sion. It has the same formula as dextrose, C 6 H 12 6 , but 
different chemical and physical properties, due to a differ- 
ent structural composition. Levulose is very sweet, and 
is found in many ripe fruits and vegetables. Its properties 



184 AGRICULTURAL CHEMISTRY 

are somewhat similar to those of dextrose, but it is more 
susceptible to the action of heat, acids, and alkalies, and 
less to the action of ferments. 

Experiment 50. — Levulose and reducing sugars from carrots. 
Reduce a small clean carrot to a pulp. Place the pulp in a beaker 
and add 200 cc. water. After half an hour, filter, heat the nitrate 
for fifteen minutes, and then filter a second time. Evaporate 50 cc. 
of the filtrate nearly to dryness. Test a portion with Fehling's 
solution as in Experiment 49. 

Questions. — (1) How was sugar separated from the carrots? 
(2) What was the result when the filtrate was heated, and what 
compounds were precipitated ? (3) Describe the appearance of the 
concentrated filtrate. (4) What reaction was obtained with Feh- 
ling's solution ? (5) How does levulose differ in composition and 
properties from dextrose ? 

252. Miscellaneous Sugars. — A number of sugars that 
do not belong either to the dextrose or sucrose group 
are found in plants. Raffinose, for example, is a sugar 
present in beets and other vegetables in small amounts. 
It can be converted into dextrose sugars by treatment 
with dilute acids. 

253. Optical Properties of Sugar. — Sugars are charac- 
terized as optically active or inactive. Those which 
have the power of turning a ray of polarized light to the 
right are called dextrorotatory, while those which turn the 
ray to the left are called levorotatory. Polarized light 
has no action upon the inactive sugars. This principle 
is taken advantage of in the commercial testing of sugar 
by means of the polariscope, which is a piece of apparatus 
so constructed that the number of degrees which a ray of 
polarized light is diverted in passing through a solution 
of sugar can be accurately measured, and the purity of 
the sugar determined. A given weight of pure sucrose 
dissolved in a definite amount of water always turns a ray 



ORGANIC COMPOUNDS OF PLANTS 



185 



of polarized light a definite number of degrees which are 
accurately measured by the polariscope. Any decrease 
in purity influences proportionally the angle of diver- 
gence of the polarized light. Hence, if the angle of 




Fig. 78. — Polariscope 

divergence of a commercial sugar is determined, its 
purity is likewise determined. 

254. Sugar-beets are usually paid for on the basis 
of their content of sugar and purity of juice. For sugar- 
making purposes, the higher the content of sugar and the 
purer the juice, the more valuable the beets. Ordinarily, 
sugar-beets contain from 1 2 to 1 6 per cent sugar ; occasion- 
ally as low as 8 and as high as 20 per cent. In addition 
to sugar, the beet juice has other solids, as small amounts 
of organic acids, albumin, and pectin. When the content 
of solid matter is 20 per cent and 16 of the 20 parts are 
sugar, the juice has a purity coefficient of 80 (j% X 100). 

255. Food Value of Sugar. — When properly combined 
with other foods, sugar is a valuable nutrient for the pro- 
duction of heat and energy. Like starch, it is incapable 
of sustaining life unless associated with nitrogenous 



l86 AGRICULTURAL CHEMISTRY 

compounds. One pound of sugar, when burned, yields 
i. 5 pounds of carbon dioxid and 0.58 pound of water. 

C12H22O11 + 24 O = 12 C0 2 + 11 H 2 0. 

In a ration, sugar is considered as having the same 
caloric value as starch, viz., 1 pound yields i860 calories. 

256. Gums. — Closely related to the sugars are the 
gums, like gum arabic, and those which exude from 
peach and cherry trees. In the seeds also of many grains 
there are gum-like bodies. When treated with dilute 
acids, the gums are converted into dextrose sugars and 
acid products. Bassorin, or mucilage, as flaxseed muci- 
lage, is found in a few seeds and fruits. The formula 
for some of the gums is the same as for sucrose sugars 
and dextrose. 

257. Pentosans. — The pentosans are a class of carbo- 
hydrates present in liberal amounts in many plants. They 
are insoluble, and aid the cellulose in giving form and 
structure to plant tissues. When acted upon by dilute 
acids, the pentosans are rendered soluble, while true 
cellulose is insoluble. They are called pentosans because 
they yield a sugar which contains five atoms of carbon 
in the molecule. When acted upon by the digestive 
fluids they are rendered soluble and available as nutrients. 
In some fodders they form a large part of the nitrogen- 
free extract. The digestible pentosans are considered as 
having the same food value as other digestible carbohy- 
drates. The percentage amounts of pentosans in some 
common foods are approximately as follows : 

Per cent. 

Hay, timothy 20 

Linseed meal 1 2 to 1 5 

Wheat bran 1 7 to 2 2 

Wheat 4 to 6 



ORGANIC COMPOUNDS OF PLANTS 1 87 

Per cent. 

Oats 12 

Corn 5 

Barley 5 to 7 

Flour trace 

258. Pectin Bodies are found in many ripe fruits and 
vegetables. They are jelly-like substances, which are 
soluble in hot water, and are commonly known as fruit 
jellies. When treated with dilute acids, digestive fluids, 
and other reagents, the pectin bodies are converted into 
dextrose sugars and other products. Potatoes, turnips, 
beets, and all fruits contain pectin. In unripe fruits, 
and in some uncooked vegetables, the pectin is in acid 
forms which are insoluble and indigestible. In the last 
stages of ripening, the pectin of fruits and vegetables 
undergoes a change to soluble forms. Soluble pectin is 
considered to have the same food value as soluble car- 
bohydrates. 

Experiment 57. — Soluble pectin from potatoes. Reduce a small 
clean potato to a pulp. Squeeze the pulp through a clean cloth 
into a beaker, add 10 cc. H 2 0, and heat on a sand bath to coagulate 
the albumin. Filter; add a little hot water if necessary. To the 
filtrate add a little alcohol. The precipitate is soluble pectin. 

Questions. — (1) Is the pectose from the potato soluble ? (2) Is 
pectose coagulated by heat ? (3) Is it soluble in alcohol ? (4) In 
what ways does pectin differ from sugar ? (5) In what ways does 
it resemble sugar ? 

259. Nitrogen-free Extract. — In the analysis of plants 
and foods, the chemist determines the percentage of water, 
ash, crude protein, ether extract, and crude fiber, and 
then classes the remainder in one group or division 
called nitrogen-free extract. Wheat, for example, con- 
tains : 



l88 AGRICULTURAL CHEMISTRY 

Per cent. 

Water 9. 25 

Ash 2.95 

Crude protein 13-25 

Ether extract "2.20 

Crude fiber 2.25 

Total 29.90 

100 — 29.90 = 70.10 per cent nitrogen-free extract. 

The nitrogen-free extract compounds contain no 
nitrogen ; they are nitrogen-free or non-nitrogenous, 
and are soluble in dilute acids and alkalies. The nitrogen- 
free extract of wheat is principally starch ; in some 
foods, as carrots, it is largely sugar. In human foods, 
it is mainly carbohydrates as starch and sugar, while in 
animal foods, it consists of pentoses and a large number 
of compounds, dissimilar in character and food value. In 
plant bodies, the nitrogen-free extract usually constitutes 
the largest of any of the groups of compounds. Meats 
and animal products, except milk, contain very small 
amounts. 

Fats 

260. Presence in Plants. — Fats and oils form one of 
the subdivisions of the non-nitrogenous compounds of 
plants. Fat is in nearly all plants, but in smaller amounts 
than the carbohydrates. The fat in plants is produced 
from starch. For example, in flax, there is more starch 
than fat when the plant is growing, but in the mature 
plant there is more fat than starch, due to the starch 
being converted into fat. This change of starch to fat 
can take place only in plant cells ; fat, as yet, cannot 
be made synthetically. During germination, the fat 
of seeds reverts to starch. While fat is present in nearly 



ORGANIC COMPOUNDS OF PLANTS 1 89 

all parts of plants, it is most abundant in the seeds, as 
flax, rape, and cotton, which are often called oil seeds. 
Fat occurs in the form of minute oil globules within the 
plant cell-, and is removed mechanically by aid of heat 
and pressure, as in the manufacture of linseed, rape, 
cottonseed, and other oils. It is also extracted by means 
of solvents, as benzine and carbon disulfid. In roots 
and stems, fat is found only in traces. It is often in the 
form of a waxy coating on leaves, while in nuts it is stored 
in large amounts in the kernel. 

261. Physical Properties. — Fats are all characterized 
physically by being insoluble and of a lower specific 
gravity than water. There are many separate fats 
with individual characteristics, and each having its own 
specific gravity and melting point. As commonly found, 
they are not simple bodies, but mechanical mixtures of 
various fats, as stearin, palmitin, and olein. The fats are 
all soluble in ether, chloroform, and turpentine, and differ 
in physical properties according to the proportion and 
kinds of fats. When examined under the microscope, 
some have optical properties and definite crystalline forms. 

262. Chemical Composition. — Fats are all charac- 
terized by having a high per cent of carbon and a low 
per cent of oxygen. For example, in stearin, C57H110O6, 
there are in the molecule 57 atoms of carbon and 6 atoms 
of oxygen. In starch and carbohydrates in general, the 
per cent of oxygen is greater, and of carbon less, than in fats. 

Ultimate Composition of Fats. 

Stearin. Palmitin. Olein. Starch. 

Per cent. Per cent. Per cent. Per cent. 

Carbon 77.6 75.9 77.4 44.44 

Hydrogen 12.4 12.2 n. 8 6.17 

Oxygen 10.0 11.9 10.8 49-39 



190 AGRICULTURAL CHEMISTRY 

Fats are organic salts, the basic part consisting of the 
glycerol radical C 3 H 5 , which is combined with a fatty acid. 
Glycerin is the basic constituent common to all fats. 
One fat, as stearin, differs from another, as olein, by 
containing a different fatty acid in combination with the 
glycerol radical. When the simple fats are separated into 
their component parts, the acids formed are : stearic, 
palmitic, oleic, and butyric. 

Some of the fatty acids, as stearic and palmitic, are 
solids, while others, as butyric, are volatile. Those fatty 
acids which distil with boiling water are called volatile 
fatty acids. Butter, for example, contains nearly 5 per 
cent of volatile fatty acids, present mainly as butyric 
acid combined with the glycerol radical. Some of the 
fats undergo fermentation and become rancid, as butyrin 
in butter, while others slowly take up oxygen from the 
air and undergo oxidation. The chemical and physical 
properties of the fats in plants and foods are determined 
by the kinds and amounts of the separate fats. Olein, 
stearin, and palmitin are always present in larger amounts 
than are other fats. 

263. Stearin (C 5 7Hiio0 6 ) is a solid fat with a high melt- 
ing point, 69. 4 C. Beef and mutton tallow and animal 
fats in general are composed mainly of stearin. When 
pure, it is a white and tasteless body, and has a definite 
crystalline structure. Stearin predominates in all hard 
fats. 

264. Palmitin (CsiHggOe) is a white, solid fat obtained 
from butter, palm oil, and human fat. When chemically 
pure, it is tasteless, and crystallizes in the form of tufts 
and needles. It has a melting point of 63 C. Its 
general properties are somewhat similar to those of 
stearin. 



ORGANIC COMPOUNDS OF PLANTS 191 

265. Olein (C57H104O6) at moderate temperatures is a 
liquid. It solidifies at 4 C. Olein predominates in the 
oil of fish, as sperm oil and cod-liver oil. It is also found 
to a great extent in many vegetable oils, as olive oil. 
Whenever olein predominates, the fat is a liquid. 

266. Miscellaneous Fats. — In addition to the three 
fats mentioned, there are others, as butyrin, the charac- 
teristic fat of butter, and linolein, the characteristic fat 
of flaxseed. 

267. Saponification is a chemical change brought about 
by the action of an alkali, as potash or soda, upon a fat. 
An exchange takes place between the glycerol of the fat 
and the metal of the alkali. Glycerin is a base, but 
potash is a stronger base ; hence the potash replaces the 
glycerol and forms salts, as potassium stearate or palmi- 
tate, according to the fat used. 

Experiment 52. — Saponification. Weigh about 20 grams of lard 
into an evaporator. Melt the lard, but do not heat above 50 C. 
Dissolve 10 grams NaOH in about 40 cc. water in a beaker. (Do 
not let the NaOH come in contact with the scale pan.) Add this 
solution to the evaporator, stirring constantly, and leave the evapo- 
rator on the warm sand bath, with a low flame underneath, for 40 
to 50 minutes. Then place on the sand bath in the desk until the 
following day, when a good soap should have formed. Dissolve a 
little of the soap thus produced in a test tube with 20 cc. water. 
Divide the solution into two parts ; to one add a little salt, and to 
the other a few drops of HC1. 

Questions. — (1) Why was NaOH used in this experiment, and 
what portion of the fat did it replace ? (2) What other materials 
could be used in place of NaOH ? (3) What influence did the salt 
have upon the soap solution ? (4) What was the result when HC1 
was added to the soap solution ? (5) Why is it necessary to weigh 
both the lard and the NaOH ? (6) What would be the result if 
the fat and alkali were taken in different proportions from those 
used in this experiment ? (7) Why does soap form an insoluble 
mass with hard waters ? 



192 AGRICULTURAL CHEMISTRY 

268. Fatty Acids. — Formic acid, found in pine needles 
and in red ants, has the formula H 2 C0 2 , which is also 
written HC0 2 H. Acetic acid has the formula H . CH 2 . 
C0 2 H, and differs from formic acid simply in containing 
CH 2 more than found in formic acid. If CH 2 were added 
to acetic acid, H . C 2 H 4 . C0 2 H, propionic acid would be 
produced. This is present in some plants. In like 
manner, butyric acid can be obtained from propionic 
acid. By the addition of CH 2 , about twenty acids can be 
formed in the way described. This list includes palmitic, 
stearic, and other acids found in fatty bodies and named 
fatty acids ; various of these are present in nearly all 
foods. When a series of compounds, like the fatty acids, 
shows a uniform difference between two adjacent members 
the term homologous series is employed. 

269. Waxes. — Wax is similar in composition to fat, 
but contains an ethyl radical in place of the glycerol 
radical. Beeswax, for example, is composed of palmitic 
acid and ethyl radicals. Waxes, like fats, undergo saponi- 
fication and are considered as having the same food value. 

270. Food Value of Fat. — Fat is the most concentrated 
non-nitrogenous nutrient of foods. On account of con- 
taining such a large amount of carbon and so little oxygen, 
fat, when either burned or oxidized as food, produces 
2.25 times more heat than the same weight of starch or 
sugar. One gram of fat yields 9.2 calories, and 1 pound, 
4225 calories. The fact that so much more heat is pro- 
duced from the oxidation of fat is apparent when the 
products of oxidation of starch and fat are compared. 

Stearin. 
C 5 7H 110 O 6 + 163 O = 57 C0 2 + 55 H 2 0. 
890 2508 990 

1 pound of fat produces 2.8 pounds C0 2 + 1.1 pounds of water. 



ORGANIC COMPOUNDS OF PLANTS 193 

Starch. 

C 6 H 10 O5 + 12 O = 6 C0 2 + 5 H 2 0. 
162 264 90 

1 pound of starch produces 
T.6 pounds C0 2 + 0.56 pound H 2 0. 

890 parts, by weight, of fat produce, when burned, 
2508 parts, by weight, of carbon dioxid and 990 parts 
of water. 162 parts, by weight, of starch produce 264 
parts, by weight, of carbon dioxid and 90 parts of water. 
One pound of fat yields 2.8 pounds of carbon dioxid and 
1.1 pounds of water, while one of starch yields 1.6 of car- 
bon dioxid and 0.56 of water. Fat produces approxi- 
mately 2.25 times more heat than starch. 

271. Amount of Fat in Plants and Foods. — The 
amount of fat in various plant substances ranges from a 
few hundredths of 1 per cent in tubers to 35 per cent 
and more in flaxseed. Of ordinary grains, oats and corn 
are the richest in fat and contain from 3.5 to 5 per cent, 
while wheat and rye have about 2 per cent each. In 
hay the amount of pure fat is less than 2 per cent, and 
in straw it is less than 1 per cent. In nearly all food 
products the per cent of pure fat is included with the 
ether extract. 

Experiment 53. — Fat from wheat germ. Place 2 grams wheat 
germ in a test tube, and add gasoline until the test tube is about 
one third full. Cork and shake at intervals of three or four minutes. 
Do not let the gasoline come near the gas flame. Filter into a clean 
porcelain dish, and place the dish in an open window until the gaso- 
line is evaporated. Observe the residue of fat. 

Experiment 54. — Fat from yolk of egg. Repeat the preceding 
experiment, using one fourth of the yolk of a hard-boiled egg, and 
5 cc. ether instead of gasoline. 

Questions. — (1) What was the solvent used for separating the 
fat from the wheat germ ? (2) From the yolk of the egg ? (3) De- 
scribe the fat obtained from the wheat germ. (4) From the yolk 
o 



194 



AGRICULTURAL CHEMISTRY 



JBS^ 



of the egg. (5) How were the solvents removed in these experi- 
ments ? (6) Are fats volatile bodies ? (7) Why do fats obtained 
from different sources vary in appearance and properties ? 

272. Ether Extract. — The term ether extract is applied 
to that class of compounds which is soluble in ether. In 
the case of human foods, the ether extract consists largely 

of fats and oils with variable 
amounts of waxes, resins, chloro- 
phyll, vegetable coloring matters, 
and nitrogenous and phosphorized 
bodies, as lecithin. The value of 
the ether extract depends entirely 
upon its source ; in milk, meats, 
and cereals and their products, the 
ether extract is nearly pure fat, 
while in many vegetables it is less 
than half fat. Methods of chemi- 
cal analysis have not, as yet, been 
sufficiently perfected to allow the 
separation and determination of 
the pure fat of all materials. 
The ether extract is obtained by 
weighing a small amount of the 
dry material in tube 3 (Fig. 79), 
which is then placed in a glass 
extractor connected with a small 
weighed flask containing ether. 
The flask is immersed in a water 
bath heated by a gas burner, the 
ether is volatilized, and the vapor 
Fig. 79— Ether extractor. p asses through openings 2 and 4 
into the condenser, where it is cooled and falls back in 
drops from point 4 on the substance at 5. The ether 




ORGANIC COMPOUNDS OF PLANTS 195 

percolates through the substance and returns to the flask. 
The fats and ether soluble bodies are not volatilized, but 
remain in the flask while the ether is vaporized and 
condensed again and again. After the extraction is 
completed, the ether is distilled from the flask, the ether 
extract dried and weighed, and the percentage amount 
calculated. While the process appears to be simple, it is 
difficult to control, because even after many days' extrac- 
tion, certain materials will continue to give up ether extract, 
and unless unusual care is taken some of the fats are 
oxidized. Then, too, the ether extract is liable to be 
contaminated with impurities if ether of a high degree of 
purity is not used. When the determinations are made 
under uniform conditions, the results are comparable and 
are of value when properly interpreted. 

Organic Acids 

273. Occurrence in Plants. — In all plants and vege- 
table foods, there are bodies known as organic acids. 
An organic acid, like all acids, contains hydrogen which 
can be replaced by a metal (see Section 75). The nega- 
tive radical of the acid contains carbon, hydrogen, and 
oxygen. For example, in tartaric acid, H2C4H4O6, the 
H 2 can be replaced by a metal ; C 4 H 4 6 is the tartaric 
acid radical. Organic acids, like mineral acids, are neu- 
tralized by bases. 

Tartaric Potassium 

acid. tartrate. 

2 KOH + H 2 C 4 H 4 6 = K 2 C 4 H 4 6 + 2 H 2 0. 

As a rule, the organic acids are not present in a free 
state, but are combined with base-forming elements, as 
potassium and calcium, forming organic and acid salts. 



196 AGRICULTURAL CHEMISTRY 

In plants the organic acids are mainly in solution, as in 
the sap. When the plant matures, they are used either 
for the construction of other organic compounds, or are 
neutralized by bases to form insoluble salts, as calcium 
oxalate, and deposited as crystals in the leaves. A small 
amount of acid is found in all mature seeds, and during 
germination, some of the carbohydrates are converted 
into acids. In green vegetables and small fruits the 
organic acids are found more liberally than in the seeds 
of grains ; in the leaves and stems of matured plants 
there is but little acid. Some of the organic acids from 
fruits are of commercial value, as crude tartaric acid or 
argol in grapes, from which cream of tartar is pre- 
pared. There are a large number of organic acids found 
in plants and food materials, and in the study of organic 
chemistry these acids constitute an important part. In 
this work, only a few of the more common organic acids 
are considered. 

274. Tartaric Acid is the characteristic acid of grapes. 
It is also found in small amounts in pineapples, cucum- 
bers, and potatoes. It can be produced in the laboratory 
by oxidation of milk sugar and other carbohydrates. 
Crude tartar or argol, from which commercial cream of 
tartar is made, is deposited when grape juice ferments. 
When tartaric acid is neutralized with bases, tartrates 
are formed. Sodium potassium tartrate (Rochelle salt) 
is one of the most important salts of tartaric acid. 

275. Malic Acid occurs in many vegetables and small 
fruits, as tomatoes, currants, and strawberries. It is the 
organic acid found most abundantly in small fruits. 
Malic acid can be produced from tartaric acid by the 
action of hydrochloric acid. 

276. Succinic Acid is found in many plants, and also 



ORGANIC COMPOUNDS OF PLANTS 197 

in animal tissues. Small amounts of this acid are formed 
when dextrose undergoes alcoholic fermentation. Suc- 
cinic acid occurs also in soils, particularly those of a peaty- 
character. It can be produced from malic acid by the 
action of hydrochloric acid. Chemically, the three acids, 
tartaric, malic, and succinic, are closely related. 

277. Oxalic Acid is found in small amounts in nearly 
all plants, particularly those of the oxalis variety. In 
some plants, it is present in sufficient amounts to be 
poisonous. Oxalic acid can be produced, in the labora- 
tory, by the action of nitric acid upon sugar and other 
carbohydrates. 

278. Citric Acid is in lemons and many small fruits, 
also in small amounts in peas, beans, vetches, and lu- 
pines, and with malic acid in cherries, strawberries, and 
currants. 

Experiment 55. — Citric acid from lemons. Measure with the 
pipette 10 cc. of the prepared lemon juice solution. Dilute with 
about 25 cc. distilled water, and add 5 to 7 drops phenolphthalein 
indicator. Then add dilute KOH from the burette until a faint 
pink tinge remains permanent. The KOH is made by dissolving 
5 gm. in 100 cc. distilled water and the phenolphthalein indication 
by dissolving a little of the powder in dilute alcohol. The lemon 
juice solution is prepared by diluting clear lemon juice with ten times 
its bulk of distilled water and filtering. 

Questions. — (1) Why was KOH used in this experiment? 
(2) What chemical change took place when KOH was added to the 
diluted lemon juice ? (3) What change in color was observed ? 
(4) What was the final product in this experiment ? (5) How does 
this experiment compare in principle with Experiment 10? 

279. Tannic Acid. — In many seeds and leaves of 
plants there are bitter astringent compounds, as tannin 
and tannic acid. They may lessen the value of a food 
because they retard the natural process of digestion. 



I98 AGRICULTURAL CHEMISTRY 

Tannic acid is not found in food plants in any appre- 
ciable amount. Commercially, the tannins are valuable 
for the tanning of leather and for other purposes. Tannin- 
yielding plants are occasionally grown as marketable 
crops. 

280. Function and Food Value of the Organic Acids. — 
The organic acids of plants are valuable mainly because 
they impart palatability to foods and exert a favorable 
influence upon digestion by stimulating the secretion and 
flow of the digestive fluids. Many of the organic acids 
have medicinal properties, and some, as oxalic acid, are 
poisonous. The organic acids cannot be considered heat- 
or flesh-producing nutrients, but simply food adjuncts. 
In plants, they take an important part in the assimilation 
of the mineral elements of plant food, and the production 
of new tissue. The acid sap comes in contact with the 
soil particles, dissolving the plant food, which is then 
absorbed by osmosis. 

Essential Oils 

281. General Properties. — The essential or volatile 
oils are the compounds which impart characteristic taste 
and odor to plants. They differ from the fixed oils or 
fats by completely volatilizing when heated, and leaving 
no permanent residue on cloth or paper. They also have 
entirely different chemical composition from the fats. 

282. Occurrence. — Volatile or essential oils are found, 
in some form, in nearly all plants, particularly during 
growth. In some fruits and seeds they impart charac- 
teristic flavor and give individuality to the material. 
Oil of lemon, oil of cedar, and oil of nutmeg are examples 
of essential oils. In nearly every plant, one or more of 
the essential oils is present at some period of growth. 



ORGANIC COMPOUNDS OF PLANTS 1 99 

283. Chemical Composition and Properties. — The es- 
sential oils are mixed bodies, many of them belonging 
to the aromatic series of compounds (see Section 138). 
According to chemical composition, they may be divided 
into four groups, and each group in turn into a number of 
subdivisions. 

Groups. Examples, 

i. Terpenes, Ci Hi 6 Oil of lemon, oil of turpentine. 

2. Cedrenes, Ci 5 H 24 Oil of cedar, oil of cubeb. 

3. Aromatic aldehydes Oil of cinnamon, oil of almond. 

4. Etherical salts Pineapple and fruit flavors. 

The essential oils are separated from plants by distil- 
lation. At moderate temperatures, most of them are 
liquids, insoluble in water, but soluble in alcohol. When 
the terpenes and cedrenes oxidize, they produce resinous 
deposits from which turpentine is obtained (see Section 
135). The aromatic aldehydes form a homologous 
series, beginning with benzoic aldehyde, C 6 H 5 . CHO, 
and are present in many plants and fruits, impart- 
ing flavor. Ethyl formate, C 2 H 5 . HC0 2 , peach flavor, 
ethyl butyrate, C 2 H 5 . C 4 H 7 2 , pineapple flavor, and amyl 
valerate found in apples are some of the common 
etherical salts. 

284. Essential Oils of Agricultural Crops. — When hay 
is cut, the odor produced is due to a volatile oil. This 
is lost when hay is overcured or exposed to leaching 
rains. The characteristic odor of clover, particularly 
pronounced in sweet clover, is that of an aromatic body. 
The odors of all fodder crops are imparted by characteris- 
tic essential oils. In the preparation of hay and fodder 
crops, it should be the aim to prevent, as far as possible, 
any loss of essential oils. This can be accomplished by 
cutting the fodder before it is overripe, and then avoiding 



200 AGRICULTURAL CHEMISTRY 

bleaching and leaching. Rape, turnips, cabbage, parsley, 
and onions contain essential oils. 

285. Synthetic Production of Essential Oils. — Nearly 
all the essential oils found in fruits, as pineapple flavor, 
peach flavor, and vanilla, may be produced synthetically 
in the laboratory. They are definite chemical com- 
pounds, and it is only necessary to bring together, under 
right conditions, their radicals or component parts for 
them to unite and form these compounds. Pineapple 
flavor is ethyl butyrate. The acid constituent of this 
salt, butyric acid, is found in stale butter, while the basic 
part of the radical is in ether and alcohol. The chemical 
union of butyric acid and the ethyl radical gives ethyl 
butyrate or pineapple flavor. In fact, nearly all of the 
commercial fruit flavors are laboratory products. When 
properly made, they are identical with the same flavors 
as found in fruits, but frequently they contain traces of 
acid or alkaline products used in their preparation. 

286. Amount of Essential Oils in Plants. — The 
amount of essential oils in plants and foods is small, less 
than 1 per cent, and usually only a fraction of a per cent. 
This, however, is sufficient to give characteristic taste. 

287. Food Value. — Some of the essential oils of fodders, 
like the organic acids, exert a favorable influence upon 
digestion by imparting palatability and stimulating the 
secretion and flow of the digestive fluids. They are 
not heat- or muscle-forming nutrients, but simply food 
adjuncts. Some of the essential oils have medicinal 
properties, while others, as oil of bitter almonds, are 
poisonous. 

Experiment 56. — Essential oil from tea. Place o. 5 gram tea in 
a small flask, and add 50 cc. water. Connect the flask with a de- 
livery tube, one end of which leads into a test tube containing 



ORGANIC COMPOUNDS OF PLANTS 



201 



water. Arrange apparatus as shown in Fig. 80. Apply heat and 
distil 3 to 5 cc. Observe odor of distillate, which is that of the vola- 
tile oil of tea. Repeat this experiment, using sweet or red clover. 




Fig. 80. — Preparation of essential oils. 

288. Miscellaneous Compounds of Plants. — Not all 

of the non-nitrogenous compounds in plants are included 
in the subdivisions : carbohydrates, fats, organic acids 
and essential oils. The most important and common 
ones, however, are included in the above list. There 
are many others which, for convenience of classification, 
are called miscellaneous or mixed compounds. 



202 AGRICULTURAL CHEMISTRY 

289. Relationship of Non-nitrogenous Compounds of 
Plants. — A marked general relationship exists between 
many of the non -nitrogenous compounds. For example, 
the various carbohydrates may undergo chemical changes 
in which one form is converted into another. Starch 
can be changed to cellulose, sucrose, maltose, or any 
other carbohydrate, and conversely cellulose can be 
converted into starch or other similar compounds. These 
changes take place in plant growth, particularly during 
germination of the seed, and are brought about by the 
action of ferment bodies, which cause either addition or 
elimination of water from the molecule, as 

2 C6H10O5 + H2O == C12H22O11. 

Not all of these reactions can take place in the laboratory. 
Starch may be changed to glucose or maltose, and sucrose 
may undergo inversion and form invert sugars, but 
sucrose cannot be made in the laboratory; neither can 
starch or cellulose be made from glucose. During ger- 
mination, some of the carbohydrates are converted into 
organic acids. 

The fatty acids are the characteristic constituents of 
fats. In germinating seeds, fat is formed from starch by 
the addition of oxygen. The pectose substances are 
capable of being separated in the laboratory into glucose 
and acid products. Likewise the glucosides may be split 
up into glucose and acid bodies. In fact, the various 
non-nitrogenous compounds of plants, considered as a 
whole, are more or less related in chemical composition. 

290. Food Value of the Non-nitrogenous Com- 
pounds. — As a class, the non-nitrogenous compounds 
are valuable as heat- and energy-producing nutrients. 
They do not all have the same caloric or fuel value ; for 



ORGANIC COMPOUNDS OF PLANTS 203 

example, a gram of starch yields 4.2 calories, while a gram 
of fat yields 9.2. As a rule, the more concentrated the 
compound in carbon, the greater its fuel value. When 
properly associated and combined with the nitrogenous 
compounds, the non-nitrogenous nutrients of plants may 
produce fat in the animal body. A few of the non- 
nitrogenous compounds, as the essential oils, have but 
little direct value as nutrients. Others, as some bitter 
principles and tannic compounds, may lessen the value of 
foods or impart a negative value. The carbohydrates, 
fats, and related non-nitrogenous compounds take an 
important part in the nutrition of man and animals, and 
many foods owe their value entirely to the fats and car- 
bohydrates which they contain. 



CHAPTER XXIV 
Nitrogenous Organic Compounds of Plants 

291. Amount of Nitrogenous Matter in Plants. — As 

a rule, less than 1 5 per cent of the dry matter of plants 
is nitrogenous material. In the seeds of legumes, as 
beans and peas, it amounts to about 22 per cent. In 
nearly all plants, the non-nitrogenous compounds are 
from six to ten times more abundant than the nitrogenous. 

292. Different Terms Applied to Nitrogenous Com- 
pounds. — Unfortunately, the various terms used to 
designate the nitrogenous compounds have not been 
uniformly applied. Nitrogenous compounds, proteids, 
crude protein, and albuminoids all have been used synony- 
mously, but each applies to a different class. Organic 
nitrogenous compounds and crude protein are the most 
satisfactory appellations for the entire group; proteids 
and albuminoids are subdivisions of the nitrogenous 
compounds. 

293. Complexity of Composition. — The nitrogenous 
compounds are more complex in composition than the 
non-nitrogenous. The percentage composition and for- 
mulas of nearly all the non-nitrogenous compounds of 
plants have been determined, and while the percentage 
composition and the physical and chemical properties of 
many of the proteids are known, no definite formulas 
have, as yet, been applied because of the complexity of 
their molecular structure. The nitrogenous compounds 
are composed of carbon, hydrogen, nitrogen, and oxygen, 

204 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 205 

and many contain, in addition to these, phosphorus, 
sulfur, and other elements. 

294. Classification of Nitrogenous Compounds. — For 

food purposes, the nitrogenous compounds of plant 
and animal bodies may be divided into four groups : 
(1) proteids, (2) albuminoids, (3) amides, and (4) alkaloids. 
There are a few nitrogenous compounds in plants that do 
not find a place in any of the above subdivisions. 

Proteids 

295. General Composition. — Proteids are complex 
nitrogenous compounds that contain about 16 per cent of 
nitrogen and less than 2 per cent of sulfur. The per 
cent of the different elements in protein compounds from 
various sources ranges as follows : 

Per cent. 

Carbon. . . . ; 51.2-54.7 

Hydrogen 6. 7-7.6 

Nitrogen 15. 2-18.0 

Oxygen 20. 2-23.5 

Sulfur 0.3-2.0 

It was believed, at one time, that all the various com- 
pounds called proteids had, in common, a nitrogenous 
radical in their molecule to which the name protein was 
given, but this hypothesis has not been found correct. 
The term protein has been retained, but not with its 
original meaning. 

296. Occurrence. — Proteids are found more abun- 
dant in the seeds of plants than in the leaves or other 
parts, and are always present in the active living cells of 
both plants and animals. The proteids take an important 
part in life processes, protoplasm being largely of a 
proteid nature. In the growing plant, the proteids are 



206 AGRICULTURAL CHEMISTRY 

found most abundant in the leaves; at maturity, they 
are stored up in the seed for future use of the embryo. 
The proteids occur either in a soluble form in the liquids 
of plant and animal tissues or in a semi-solid, insoluble 
condition as a part of the tissues. The proteids from 
animal and plant sources are closely related, but are not 
in every respect identical. For food purposes, however, 
they may be jointly considered. 

297. Physical Properties. — While the members of 
the proteid group differ materially, they all have certain 
physical properties in common. All are optically active 
and turn polarized light to the left. The soluble proteids, 
with the exception of peptones and proteoses, are coagu- 
lated by heat. The proteids show a wide range in solu- 
bility, but all are soluble in either acid or alkaline solu- 
tions. As a class, they do not crystallize, and are not 
diffusible, with the exception of the peptones and pro- 
teoses. 

298. Chemical Properties. — In structure the proteid 
molecule is a complex and unstable body. It is readily 
acted upon by ferments and chemicals. Nitrogen seems 
to form a weak link in the chain of elements. Proteids 
unite with acids and alkalies to form acid and alkali 
proteids. In plants, the proteids are generally united 
with small amounts of organic acids and mineral com- 
pounds, particularly phosphorus and potassium. They 
all respond to certain reactions : (1) nitric acid gives a 
permanent yellow color; (2) a solution of mercury and 
nitric acid, known as Millon's reagent, gives a brick-red 
color with the acid if heated; (3) a solution of copper 
sulfate and potassium hydrate gives a violet-colored 
solution. The proteids, found in living cells, have dif- 
ferent properties from those in dead tissue. Proteids 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 207 

readily undergo oxidation, and are chemically altered in 
the preparation of many foods. When the protein mole- 
cule is acted upon by heat, a large number of products are 
formed, as fatty acids, amides, aromatic bodies, ammonia, 
and carbohydrate-like bodies. The most common change 
which the proteids undergo is rearrangement of the atoms 
and radicals in the molecule. Coagulation of albumin 
by heat is a chemical reaction in which the atoms and 
radicals in the albumin molecule are simply rearranged 
structurally. The fact that it is possible for such a large 
class of compounds as the proteids to be composed of 
only a few common elements, and for the various members 
to have different properties, is accounted for by differences 
in structural composition. 

Experiment 57. — Testing for nitrogenous organic compounds. 
Mix 0.5 gram dry clover with enough soda lime to half fill a test 
tube. Connect the test tube with a delivery tube, one end of 
which leads into another test tube containing water. Apply heat 
for from five to seven minutes. Test the distillate with test paper. 
(Soda lime has the power to decompose proteid material and liber- 
ate the N as NH 3 . The C and O of the proteid unite and form 
C0 2 and H 2 0.) 

Questions. — (1) What reaction was obtained when the distillate 
was tested with litmus ? (2) What compound was produced which 
gave this reaction ? (3) What does this indicate that clover con- 
tains ? (4) Why was this compound liberated ? 

299. Classification of Proteids. — For purpose of study, 
the proteids may be divided into five classes: (i) albu- 
mins, (2) globulins, (3) albuminates (casein), (4) peptones 
and proteoses, and (5) insoluble proteids. 

There are some proteids that do not belong to any of 
the above divisions. Albumin, albuminate (casein), and 
insoluble proteids are the proteids found most abundantly 
in plant and animal bodies. 



208 AGRICULTURAL CHEMISTRY 

300. Albumins. — The albumins are proteids soluble 
in water and easily coagulated by heat. Egg albumin, 
serum albumin, and lactalbumin are examples of animal 
albumins. Wheat, oats, rye, and nearly all vegetables, 
when extracted with water, yield some albumin which 
can be coagulated by heat or precipitated with chemicals. 
From many vegetables, the albumin is lost when the 
material is soaked in water for any length of time. 
Potatoes, for example, lose a large amount of their albumin 
if soaked in cold water before boiling. 

Experiment 58. — Tests for albumin. In each of four test 
tubes, place a 3 cc. portion of a solution of egg albumin. To No. 1, 
add 3 cc. strong alcohol. To No. 2, add 2 cc. HN0 3 and heat ; 
when cool, add NH 4 OH. To No. 3, apply heat. To No. 4, add a 
few drops of lead acetate. 

Questions. — (1) What change occurred when the solution was 
heated ? (2) When alcohol was added ? (3) When HN0 3 was 
used and heat applied? (4) What did the Pb(C2H 3 2 )2 do? 
(5) What do these tests show in regard to the properties of albumin ? 

Experiment 59. — Albumin and allied proteids from oats. Place 
in a flask 10 grams of ground oats and 50 cc. of water. Cork and 
shake vigorously ; let stand for half an hour or until the next day. 
Filter (if not clear, refilter) and make the following tests with sepa- 
rate portions of the nitrate: (1) To 5 cc, add a few drops of tannic 
acid. (2) To 5 cc, add a few drops of lead acetate. 

Questions. — (1) What were the results when tannic acid and lead 
acetate were added? (2) Do the tests indicate any large amount 
of albumin ? (3) How do these tests compare with those of the 
preceding experiment ? 

301. Globulins form a group of proteids insoluble in 
water, but soluble in dilute salt solution. When animal 
or vegetable substances, as meat, eggs, wheat, rye, or oats, 
are treated with a dilute salt solution (NaCl), after 
removal of the albumins, soluble proteid substances called 
globulins are obtained which are coagulated by heat. 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 20Q 

There are a large number of vegetable globulins. The 
chief globulin of meat is myosin. When meat is soaked 
in a dilute salt solution, and then cooked as food, the 
myosin is extracted and lost. In strong salt solution, 
myosin and other globulins are insoluble ; hence the use 
of strong brine in the curing of meats. There are globulins 
in the blood ; and in the yolk of an egg, a globulin-like 
body, vitellin, is found. As a rule, globulins do not make 
up a very large proportion of the proteids of foods. 

Experiment 60. — Obtaining globulin from oats. To the residue 
left in the flask from Experiment 59, add 2 grams of salt and 50 cc. 
water. Shake vigorously and, after one hour, filter and make the 
same tests as in Experiment 59. Save the residue in the flask for 
Experiment 65. 

Questions. — (1) What results were obtained when the solution 
was tested with lead acetate and tannic acid ? (2) What do these 
results indicate? (3) What are globulins? 

Experiment 61. — Separation of meat globulin or myosin. Test 
as follows four 3 cc. portions of myosin solution, prepared by soak- 
ing fresh meat in a 5 per cent salt solution. To the first, add a few 
drops of alum solution. To the second, add a few drops of lead 
acetate. To the third, add salt until the solution is saturated. 
To the fourth, apply heat. 

Questions. — (1) What result was obtained with the alum solution 
and what does this indicate ? (2) What did the lead acetate and 
the salt solutions do ? (3) What was used as the solvent for the 
myosin ? (4) What is myosin ? (5) What are the properties of 
myosin ? 

302. Albuminates. — The albuminates are a group of 
proteids widely distributed in both animals and plants. 
They may be produced by the action of either dilute acids 
or alkalies upon albumins or globulins. Albuminates 
are insoluble in water, and when an acid albumin is 
neutralized with an alkali, the albuminate is precipitated. 
In like manner, an acid precipitates an alkali albumin. 



2IO AGRICULTURAL CHEMISTRY 

Casein is an albuminate present in milk, in a semi-soluble 
form combined with some of the mineral matter. Casein 
is soluble in dilute alkalies, but is precipitated by acids. 
In plants the albuminates are sometimes called vegetable 
casein. From peas, a casein-like body can be extracted. 

Experiment 62. — Separation of meat albuminate or syntonin. 
To three portions of prepared syntonin solution, add : to the first, 
Na 2 C03 until neutral, avoiding an excess, as it dissolves the precipi- 
tate ; to the second, add NaOH, a drop at a time until neutral ; to 
the third, add a few drops of lead acetate. Syntonin solution is pre- 
pared by cutting fresh meat into small pieces, and extracting it for 
four hours, in water containing a few drops of HC1. 

Questions. — (1) What result was obtained when each reagent 
was added to the syntonin solution ? (2) What was used in the 
preparation and what as the solvent for syntonin ? (3) What is 
syntonin ? (4) What are the properties of syntonin ? 

Experiment 63. — Preparation of vegetable casein from peas. 
Place in an evaporator 1 gram of pea meal, 100 cc. H 2 0, and 3 cc. 
NaOH. Heat on the sand bath, occasionally stirring. Filter. If 
the filtration is slow, pour off and use some of the clear solution. 
Neutralize with HC1 and observe. 

Questions. — (1) To what class of proteids does vegetable casein 
belong ? (2) What was used as the solvent for extracting the vege- 
table casein ? (3) What effect had HC1 ? (4) How does vegetable 
casein resemble the casein from milk in solubility and other proper- 
ties ? 

303. Peptones and Proteoses are closely related groups 
of proteids found in animal and vegetable bodies. When 
any proteid material is acted upon by the peptic and 
tryptic ferments, peptones are formed. These are 
soluble in water, and are not coagulated by heat or pre- 
cipitated by acids or alkalies. They are derived from 
other proteids by ferment action, and are the first products 
formed when the proteids of the food undergo digestion. 
In prepared or peptonized foods, the peptonizing process 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 211 

is carried on artificially. When meat undergoes curing 
or ripening, a small amount of peptones is produced. 
Peptones are present naturally in milk and also in traces 
in nearly all cereal products. When seeds germinate, 
proteoses are formed. These are never present in ordinary 
foods in any appreciable amount. 

Experiment 64. — Tests with peptones. Measure into separate 
test tubes three 5 cc. portions of peptone solution. To the first, 
apply heat and, when cool, add a few drops of tannic acid. To the 
second, add a few drops of alum solution. To the third, add 5 cc. 
alcohol. The peptone solution is prepared by treating coagulated 
egg albumin with pepsin. Five grams of commercial pepsin are dis- 
solved in 1 liter of water containing 5 drops HC1. This artificial 
pepsin solution represents the solvent power of gastric juice upon 
proteid substances. The white of a hard-boiled egg is put into a 
flask, and 250 cc. pepsin solution added ; the flask is then placed in 
a water bath which is kept at a temperature of 3 8° C. for four or 
five hours. 

Questions. — (1) What action did the pepsin have on the egg 
albumin and what was produced ? (2) What was the result when 
heat was applied in test No. 1, and how does this compare with the 
result when egg albumin was similarly treated ? (3) What effect 
did tannic acid and alum have upon the pepsin solution and what 
did they produce ? (4) What was the result when alcohol was 
added? (5) What are peptones? (6) What does this experiment 
show in regard to some of the properties of peptones ? 

304. Insoluble Proteids. — The insoluble proteids are 
present in plant and animal bodies in larger amounts 
than are any of the other proteids, and include a large 
number of similar though chemically distinct substances. 
Muscular tissue is composed largely of insoluble proteids. 
The term gluten is applied to this class of compounds 
in seeds and is a mixture of two or more insoluble proteids. 
For example, wheat gluten is composed of gliadin and 
glutenin. Gliadin is a glue-like body which binds together 



212 AGRICULTURAL CHEMISTRY 

the flour particles, and in bread-making, enables the gas 
to be retained in the dough. Glutenin is a fine, gray 
material which unites mechanically with gliadin to form 
gluten. An excess of gliadin produces a soft gluten. 

As a class, the insoluble proteids are not soluble in 
water or dilute salt solution, but are soluble in dilute 
acids and alkalies. They all undergo the peptonizing 
process and yield proteoses and peptones. Insoluble 
proteids are the most common form of proteids in 
foods. 

Experiment 65. — Obtaining insoluble proteids from oats. To 
the residue left in the flask from Experiment 60, add 2 cc. NaOH 
and 50 cc. water. After shaking and allowing half an hour (or 
until the next day) for extraction of the proteids, filter off the solu- 
tion and make the following tests: (1) Neutralize 5 cc. with HO, 
and if no precipitate appears, add a few drops of lead acetate ; 

(2) neutralize 5 cc. with HC1 and evaporate to dryness on the 
water bath. 

Questions. — (1) Why was NaOH used ? (2) What effect did the 
HC1 and lead acetate have when added to the solution, and what 
was formed ? (3) How did this precipitate of insoluble proteids 
from oats compare in amount with the globulin and albumin pre- 
cipitation in Experiments 59 and 60 ? (4) What is an insoluble 
proteid ? 

305. Food Value of Proteids. — The proteid compounds 
of plant and animal bodies serve three purposes as nutri- 
ents : (1) to produce new muscular tissue and vital 
fluids in the body, and supply material for repairing 
broken-down tissue; (2) to produce heat and energy; 

(3) to assist in the production of fat. 

The main function of the proteids is to produce new 
proteid tissue in the body, and to furnish material for 
the repair of old or worn-out proteid tissue. The vital 
fluids of the body, as blood, chyme, milk, and the diges- 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 213 

tive fluids, all contain proteids, and the animal body is 
incapable of producing any of these from either non- 
nitrogenous or amide compounds. When the food fails 
to supply sufficient protein, the body uses its reserve 
supply as long as it lasts, and then starvation results. 
When there is an excess of proteids in the food, it is 
used for producing heat or is stored in the body as fat. 
Either an excessive or a scant amount of proteids in a 
human or animal ration is not desirable or economical. 
As stated under chemical properties of proteids, Section 
298, the proteid molecule, when broken up, forms a large 
number of simpler bodies, as fatty acids and carbohydrate 
radicals ; and it is poor economy to feed proteids in 
excess and have part perform the functions of fats and 
carbohydrates. Protein is deficient in many foods, 
and when such foods are used, they should be combined 
with those rich in proteids. There are a few proteids 
which are poisonous. Some of the toxins produced 
during disease are proteids. 

306. The Amount of Proteids in Plants varies accord- 
ing to the kind of plant, stage of growth, and part of the 
plant. Seeds always contain most, and roots and stalks 
least. In wheat, oats, barley, and rye, the amount ranges 
from 10 to 15 per cent; in corn, from 9 to 12 per cent. 
Beans and peas contain about 25 per cent, clover hay, 
from 11 to 14 per cent, timothy hay and corn fodder, 
6 to 9 per cent ; while in straw there is usually less than 
4 per cent. During the early stages of growth, the dry 
matter in all plants is relatively richer in proteids than at 
maturity. This is because the proteids are formed mainly 
in the early stages, while the carbohydrates are produced 
more abundantly in the later stages of growth. 

307. Crude Protein. — This term is applied to the 



"4 



AGRICULTURAL CHEMISTRY 



nitrogenous compounds of foods, considered collectively. 

The word crude is used to distinguish this group because 

it contains various nitrogenous bodies, not proteids. 

Pure protein is a simple chemical compound, while crude 

H protein consists of a group of 

compounds of which pure protein 

is one. The albumin of eggs and 

I JQ milk and the gluten of grains are 

ff*J p— — — ^-===s/-z types of pure proteids. In many 

foods, as potatoes, roots, and 
fruits, less than half of the crude 
protein is pure protein. Crude 
protein, from different sources, 
is unlike in character, composi- 
tion, and, to a certain extent, in 
food value. Less is known of 
its composition and food value 
than of any other class of nu- 
trients in foods. 

In the analysis of plant and 
animal substances, the chemist 
first determines the per cent of 
total organic nitrogen and then 
multiplies this by 6.25 to obtain 
the equivalent amount of crude 
protein. This is because the proteids contain, on the 
average, about 16 per cent nitrogen, or there is about one 
part of nitrogen to every 6.25 of protein (100 4- 16 = 6.25). 
The nitrogen can be determined with accuracy ; in fact, 
the method for its determination is one of the most accu- 
rate in chemistry. In brief, the method consists in first 
digesting a small weighed amount of material in a flask 
with sulfuric acid to oxidize the organic matter and con- 




Fig. Si. — Digestion apparatus 
used in the determination of 
nitrogen. 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 21 5 

vert the nitrogen into ammonium sulfate (see Fig. 81J. 
The nitrogen, in the form of ammonium sulfate, is then 




Fig. 82. — Distillation apparatus used in the determination of nitrogen. 

liberated as free ammonia, distilled, and its amount 
determined (see Fig. 82). 

Albuminoids 

308. Composition of Albuminoids. — This term is applied 
to a class of bodies resembling proteids, but differing 
from them in composition and food value. Albuminoids 
are found in both animals and plants, but more abundant 
in animal tissue. Some albuminoids are composed of 
carbon, hydrogen, nitrogen, and oxygen, while others 
contain, in addition, phosphorus, sulfur, and other ele- 
ments. 

309. Nuclein is an albuminoid found in both plant 
and animal bodies ; it is the material of which the nuclei 
of cells are composed, and has been separated from milk, 
the yolk of egg, and white blood corpuscles, as well as 
from plant tissue. This albuminoid contains phos- 
phorus, and has been assigned the formula C2QH49X9P3O22. 
Xuclein takes an important part in the growth and life 



2l6 AGRICULTURAL CHEMISTRY 

processes of both plant and animal cells. From different 
sources it has slightly different chemical properties. It 
is probably a mixture of several bodies, and not a dis- 
tinct chemical compound. 

310. Gelatin is an albuminoid obtained from connec- 
tive tissue and bones by the action of either boiling 
water or dilute acids upon an albuminoid called collagen. 
Commercial gelatin or glue is the crude product obtained 
from animal refuse. The formula C102H151N32O39 has been 
assigned to gelatin. Gelatin contains no sulfur, and 
has a different proportion of nitrogen from proteid 
bodies. 

311. Mucin is an albuminoid found in connective 
tissue. It is the chief constituent of mucus, and imparts 
sliminess to the secretions of the mucous membrane. 
Mucin is present in the saliva from the submaxillary 
glands, and in the bile and other fluids of the body, 
particularly those of an alkaline nature. 

312. Elastin is an insoluble albuminoid found in con- 
nective tissue. Keratin is the hard, horny material in 
the nails, hoofs, and horns of animals, while chondrin is 
obtained from cartilage. A number of other albuminoids 
also are present in both animal and plant bodies. 

313. Food Value of Albuminoids. — Gelatin and most 
of the animal albuminoids undergo digestion, but cannot 
take the place of protein in a ration. An animal would soon 
die if its nitrogenous food were entirely in the form of 
gelatin. Gelatin, when combined with other nutrients, 
may, however, prevent the rapid conversion of the tissue 
proteids into circulatory proteids, and thus it aids in 
establishing a proteid equilibrium in the body. Nuclein 
and some of the nucleated albuminoids have a higher 
food value than gelatin, and are considered as having 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 21 7 

the same value as the true proteids. The gelatin albumi- 
noids conserve the proteids of the body, but do not take 
the place of proteids in the repair of worn-out tissues. 

Amides and Amines 

314. Composition and Properties. — The amides and 
amines are heterogeneous compounds found in both 
animal and plant bodies. They are less complex in com- 
position than either proteids or albuminoids, and are 
produced by replacing one or more of the hydrogen atoms 
of ammonia with an organic radical. If the radical is 
acid in character, an amide is formed ; if alcoholic or 
basic, the resultant product is an amine. Amides and 
amines are related to ammonia, as will be observed from 
the following formulas : 



/H 


/C2H3O2 


/CH3 


N— H 


N— H 


N— H 


\H 


\ H 


\H 


Ammonia. 


Amide. 


Amine. 




(Amidoacetic acid.) 


(Methylamine.) 



When the methyl group or radical replaces one of the 
hydrogen atoms of NH 3 , the product is methylamine. 
When the acetic acid radical replaces one of the hydrogen 
atoms of NH 3 , the product is amidoacetic acid. The 
amides and amines are sometimes called compound 
ammonias, and are produced in plants from ammonia 
during growth, and in animals during the digestion of 
proteids. 

315. Formation and Occurrence in Plants. — The 
amide and amine compounds in plants are found mainly 
in the early stages of growth. The young plant takes 
up from the soil simple nitrogenous compounds, as 
ammonia, then a chemical change occurs in the tissues of 



2l8 AGRICULTURAL CHEMISTRY 

the plant, and as a result, a part or all of the hydrogen 
of the ammonia is replaced, and an amide is formed. In 
the study of the composition of proteids (see Section 295) 
it was stated that the proteid molecule when decomposed 
yields amide and amine products ; consequently it would 
appear that these compounds are intermediate products 
in the production of proteids. In the early stages of 
plant growth, amides are present in greatest abundance, 
but as the plant approaches maturity, they are used 
for the production of proteids. In clover, for example, 
35 per cent of the total nitrogen is in the form of amides 
before bloom, while only 12 per cent is in the same form 
after bloom. 

316. Formation and Occurrence of Amides in Animals. 
— In the animal body, amides and amines are not formed 
from ammonium compounds, as in plants, but from 
proteids. When the proteid molecule is broken up, 
as in digestion, amides and amines are produced. Urea, 
an amide, is one of the final products in the metabolism 
of protein, and is excreted from the body in the liquid 
excrements, while amidoacetic acid is excreted with 
the solid excrements. The animal body cannot produce 
proteids from amides, or amides from ammonia. This 
elaboration or construction process can take place only in 
plants. The animal body can simply make over into 
other forms the proteids supplied in the food, or decom- 
pose them and form amides and other products. 

In animal tissues, many amides are produced during 
fermentation and decay, as methylamine, the base which 
gives the characteristic odor to fish. Methylamine is 
also found in rye fodder when the plant is at the heading- 
out stage, and imparts a fishy taste to the milk of cows fed 
upon such fodder. In meats, these compounds are 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 2IQ 

associated with other bodies, as ptomaines, which are of 
poisonous nature. Amides are also produced during 
the digestion of food, and if the intermediate products 
between proteids and amides are not completely oxidized, 
poisonous substances are formed. 

317. Food Value of Amides. — Amides do not have 
high food value compared with proteids, and cannot 
replace proteids in a ration. Amides possess only a 
secondary food value, and, like the gelatin albuminoids, 
they may to a limited extent prevent rapid waste of 
body tissue. Some give taste and character to foods, as 
asparagin in asparagus, and in meats they are the materials 
which give flavor. Some of the amides have medicinal 
properties, while others are poisonous. 

318. Amount of Amides in Foods. — In matured 
grains, less than 5 per cent of the total nitrogenous matter 
is in the form of amides, and in meats there is less than 
1 per cent. In some foods, notably roots and tubers, 
the amides constitute a third or more of the nitrogenous 
matter. In fodders, the amount depends upon the stage 
of growth at which the crop is cut. When mature, from 
10 to 15 per cent of the nitrogenous matter is in the form 
of amides, while in the early stages, there are two or three 
times as much. Amides and amines form a part of crude 
protein (see Section 307), and in comparing the crude 
protein content of foods the amount of amide nitrogen 
should be considered, because the amides are of less food 
value than the proteids. 

319. Protein Production and Disintegration. — The 
following cycle of changes takes place in the production 
of proteids in plants : 

(1) Ammonia is taken from the soil. 

(2) An amide is produced from ammonia. 



220 AGRICULTURAL CHEMISTRY 

(3) A proteid is finally formed from the amide. 
When plants are used as food, the reverse order of 
changes takes place in the animal body : 

(1) The proteid of the food undergoes digestion, and 
is made over into proteid tissue in the body. This pro- 
teid tissue is finally broken up into amides. 

(2) The amide is expelled from the body as waste 
matter. 

(3) In the soil, the amides are changed to ammonia, 
and are then ready to begin anew this cycle of changes. 

Alkaloids 

320. General Composition. — Alkaloids are nitrogenous 
organic compounds present in many animals and plants, 
but not found in any appreciable amount in food plants. 
They are basic in character and unite with acids to form 
salts, just as ammonia unites with acids to form salts. 
Quinine, for example, is an alkaloid, and with sulfuric 
acid yields quinine sulfate. Animal alkaloids are some- 
times called ptomaines and leucomaines. Vegetable 
alkaloids are generally named from the species of plant 
or source from which they are obtained, as Peru- 
vian bark alkaloids, lupine alkaloids, and opium 
alkaloids. 

321. Plant Alkaloids. — No alkaloids are found in 
cereals or ordinary food plants, though at one time it 
was supposed that oats contained such a stimulating 
material to which the name avenin was given ; later 
investigations show that there is no avenin or other 
alkaloid in oats. The alkaloids are closely related chem- 
ically to the amines, and are produced by the action of 
amido compounds upon other bodies. They are also 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 2 21 

produced by the action of fungi, as ergotin, the alkaloid 
from ergot or grain smut. While found most abundantly 
in the leaves and seeds, they occur in all parts of plants. 
Some plants are cultivated for these compounds which 
possess medicinal properties. Many poisonous weeds 
contain alkaloids, as the water hemlock and monk's 
hood. Large numbers of alkaloids are known, and since 
they possess medicinal rather than food value, they are 
of more importance to the medical and pharmaceutical 
than to the agricultural student. A few of the more 
common alkaloids and their sources are : 

Pipeline, from seeds of black pepper. 

Sinapore, from seeds of mustard. 

Vicine, from seeds of vetch. 

Nicotin, from leaves of tobacco. 

Quinine, from Peruvian bark. 

Strychnine, from strychnos bean. 

Brucine, from strychnos bean. 

Morphine, from opium (seeds of poppy). 

Lupinin, from lupin seeds. 

322. Animal Alkaloids. — In the animal body, alkaloids 
are produced by ferment action. During disease, and 
when the proteids of the food fail to undergo the natural 
chemical changes of digestion, alkaloids, or ptomaines, 
are produced which are active poisons or toxic bodies. 
When animal tissue undergoes decay, ptomaines are 
produced as the result of ferment action. In stale 
meat, fish, and cheese, there may be a number of such 
bodies. 

323. Food Value and Production. — The alkaloids 
cannot be regarded as nutrients, as they possess no direct 
food value. Medicinally, many are valuable because of 
their action upon certain nerve centers. Some lessen 



222 AGRICULTURAL CHEMISTRY 

the value of foods because they prevent the normal 
process of digestion. A few alkaloids have been made 
in the laboratory by synthetic methods, and it is believed 
that in a short time all of the more important ones will 
be produced in this way. 

324. Mixed Nitrogenous Compounds. — There are a few 
nitrogenous organic compounds in foods which do not 
belong to any of the four divisions : proteids, albuminoids, 
amides, and alkaloids. Such are called mixed nitrogenous 
compounds, and are closely related to both the nitrogenous 
and the non-nitrogenous groups. 

325. Lecithin is a nitrogenous fat. It is soluble in 
ether, and has many of the characteristics of fats. It 
contains fatty acids in combination with nitrogenous 
bases and other bodies. It is present in milk, egg-yolk, 
and in small amounts in all of the cereals. 

326. Nitrogenous Glucosides. — There are a number 
of glucosides which contain nitrogenous radicals. When 
treated with acids, they yield glucose and nitrogenous 
acid products. The nitrogenous glucosides and lecithin 
may be regarded as compounds intermediate in the 
classification of the organic compounds into nitrogenous 
and non-nitrogenous groups. 

327. General Relationship of the Nitrogenous Organic 
Compounds. — A general relationship exists among the 
nitrogenous compounds similar to that among the non- 
nitrogenous (see Section 289). Amides and amines are 
the simplest in chemical structure of the nitrogenous 
compounds, while the proteids are the most complex. 
In plants, the amides are intermediate products in the 
formation of proteids. The proteid molecule contains, 
with other bodies, amide and fatty acid radicals. Amides 
are likewise obtained from the albuminoids. Thus it 



NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 223 

appears that the amides and amines form the basal 
structure of the nitrogenous part of the molecules of 
proteids, albuminoids, and alkaloids, and these com- 
pounds differ from each other chemically, according to 
the nature and kind of radicals in combination with the 
different amide and amine compounds. 



CHAPTER XXV 
Chemistry of Plant Growth 

328. Seeds. — A seed is an embryo plant surrounded 
by reserve food materials in the form of mineral matter 
and nitrogenous and non-nitrogenous compounds. 

329. Ash of Seeds. — The proportion of ash in seeds is 
small compared with that in other parts of plants. For 
example, the wheat kernel has 2 per cent and the 
straw 7 per cent ; corn has 1.75 per cent and the stalks 
7 per cent. While seeds contain comparatively little 
ash, this ash is more concentrated in the essential elements 
than that of the other parts of plants. In the seeds are 
stored large amounts of phosphorus pentoxid, magnesia 
and potassium compounds, ash elements which are of 
greatest importance for the nutrition of the young plant; 
while in the straw are found most of the non-essential 
mineral elements, as silicon, sodium, and chlorin. The 
per cent of the various ash elements in cereals and other 
seeds is given in Section 209. The amount of ash in 
seeds is quite constant, more so than in the stems, leaves, 
or other parts of plants. In mature wheat, there is rarely 
more than 2.10 per cent or less than 1.80 per cent, while 
in the straw the ash may range from 5 to 9 per cent. 
Constancy of composition is a characteristic of the ash 
of seeds. 

330. Non-nitrogenous Compounds of Seeds. — Starch, 
cellulose, and usually fat, are the most abundant non- 
nitrogenous compounds in seeds; and sugar, gums, pen- 

224 



CHEMISTRY OF PLANT GROWTH 225 

tosans, and organic acids are present in small amounts. 
There is no regular law as to the way in which the reserve 
food is stored in seeds. Even in the same family of plants, 
the nature of this reserve food may vary between wide 
limits. Starch forms the largest proportion of the reserve 
food of cereals. In oil seeds, as flax, rape, and mustard, fat 
is the main form of non-nitrogenous food. Since fat is 
about 2.25 times more concentrated in fuel value than 
starch, it follows that in oil seeds a large amount of reserve 
material is stored in a small space. Oil seeds are, as a 
rule, small in size, but concentrated in both non-nitrog- 
enous and nitrogenous food. The cellular tissue of seeds 
is composed of cellulose and pentosan materials. The 
amount of pure cellulose is generally small. 

331. Nitrogenous Compounds of Seeds. — The nitrog- 
enous compounds of seeds are mainly in the form of 
insoluble proteids, as the glutens of the cereals. Some 
other proteids, as albumin, globulin, and proteose, are also 
present, as well as some of the albuminoids, as nuclein, 
and a small amount of amide compounds. In studying 
the carbohydrates, it was found that starch was present 
in regularly organized forms called starch granules. In 
many seeds, particularly cereals, the proteids also are 
in organized forms called aleurone grains. Under the 
microscope, the aleurone grains look like crystals. They 
are not true crystals because they are not built on a 
definite plan. An aleurone grain consists mostly of proteid 
matter, inclosed in a nitrogenous envelope. The nitrog- 
enous compounds of seeds are stored liberally in the 
germ or portion adjacent to the embryo. The amount 
of nitrogenous material in seeds is, like the ash, quite 
constant in form and amount. 

332. Chemical Changes during Germination. — All of 



226 



AGRICULTURAL CHEMISTRY 



the food materials in seeds undergo chemical changes 
during the process of germination. The chief agents 
in bringing about these changes are the various kinds 
of soluble ferments which are always present in seeds. 
The more important changes may be summarized as 
follows : cellulose to soluble carbohydrates ; starch 
to soluble forms and then to dextrose bodies ; fat to 
starch ; insoluble proteids to proteoses and a small amount 
to amides. Organic acids are produced during germi- 
nation from both nitrogenous and non-nitrogenous com- 
pounds. 

333. Change of Starch to Soluble Forms. — When 
seeds germinate, the starch is changed to soluble forms 
before it is utilized by the plantlet. During conversion 
of starch into soluble forms, the diastase ferment becomes 
active, rendering the granulose soluble, 
and finally leaving nothing but a pitted 
cellulose skeleton which is also rendered 
soluble. The change of starch into soluble 
forms and dextrose bodies is brought 
about by the action of ferments, partic- 
ularly diastase, which is found in all seeds. 
During the process of germination, some 
of the starch is oxidized, and heat is 
produced. Not only starch, but other 
carbohydrates, as pentose and cellulose, 
undergo similar change during germina- 
tion. 

Experiment 66. — Reaction of germinating 
seeds. Fill a cylinder with moist sawdust ; then 
place upon the sawdust between two blue litmus papers a few wheat 
seeds. Cover with a little of the moist sawdust. After germina- 
tion, examine the litmus paper. 

Questions. — (1) What was the reaction of the rootlets upon the 




Fig. 83. 



CHEMISTRY OF PLANT GROWTH 227 

litmus paper ? (2) How was the material which caused the reaction 
produced ? (3) What does this suggest as to the solvent action of 
plant roots ? (4) How would the dry matter of the germinated seeds 
compare with that of the original seeds ? 

334. Change of Fats to Starch. — In germination, the 
fats are first broken up into fatty acids and then converted 
into starch, soluble carbohydrates, as dextrin and invert 
sugars. It is estimated that 887 parts of fat will produce 
1700 parts of starch simply by the addition of oxygen 
from the air. Ferment action causes this change to take 
place. In the oil seeds, about twice the amount of reserve 
food is stored in the same space in the form of fat as in 
other seeds in the form of starch. 

335. Change of Insoluble Proteids to Soluble Forms. 
— The proteid compounds of seeds, present mainly in 
insoluble forms, are converted by ferment action into 
soluble forms as proteoses. Some of the soluble proteids 
are broken down into amides which are then in condition 
to be transported through the plant tissues and used as 
building material. After passing through the cell walls, 
these compounds are reconstructed into proteids. There 
is always a slight loss of nitrogen in the germination of 
seeds. 

336. Germination of Seeds and Digestion of Food 
Compared. — The chemical changes which take place in 
the germination of seeds are similar to those which occur 
in the digestion of food. In the germination process, 
starch, fat, and proteids are changed by ferment action 
to soluble forms. The diastase and peptonizing ferments 
are among the most active in producing the chemical 
changes in both germination and digestion processes. 
Seed germination is, in part, a digestion process. 

337. The Necessary Conditions for Germination are : 



2 28 AGRICULTURAL CHEMISTRY 

(i) moisture, (2) heat, and (3) oxygen. The same con- 
ditions which produce decay are necessary for germination. 
The temperature required for germination ranges between 
comparatively narrow limits : 

Wheat 35° F. to 104 P. 

Barley 38 F. to 104 F. 

Peas 44. 5 F. to 102 F. 

Corn . .48° F. to 115 F. 

The necessity of oxygen for germination is shown by 
the following experiment : When seeds are put into 
water those that float are generally the only ones that 
germinate. A few of those that sink may germinate, 
getting their oxygen from that dissolved in water. If a 
current of air is passed through the water all the seeds 
will germinate. Oxygen is necessary during germination 
in order to oxidize some of the reserve material and 
produce heat. Seeds, in germinating, always lose weight. 
Malted or germinated seeds weigh less than the original 
seeds. 

338. Heavy- and Light-weight Seeds. — While seeds 
are quite constant in chemical composition, there is 
a slightly greater amount of total plant food in heavy- 
than in light-weight seeds. In case of wheat, experiments 
show that the additional reserve food in heavy-weight 
seeds favorably influences the growth of the crop, particu- 
larly when the soil is slightly deficient in available plant 
food. The additional reserve food in heavy-weight 
seeds enables the young plant to reach a more advanced 
stage of growth before being compelled to collect and 
assimilate food from the soil. When the soil is in a high 
state of fertility the difference in results between light- 
and heavy-weight seeds is less noticeable. 



CHEMISTRY OF PLANT GROWTH 229 

Experiment 67. — Calculation of plant food in seeds. Weigh 
100 plump, well-formed wheat kernels. Then from this weight and 
the following data compute the grams of nitrogen, phosphoric acid, 
and potash per 1000 wheat kernels. Wheat contains about 2 per 
cent nitrogen and 90 per cent dry matter. The dry matter con- 
tains about 2 per cent ash, approximately 50 per cent of the ash 
being P 2 5 , and 33 per cent K 2 0. Repeat the experiment, using 
100 shrunken wheat kernels. Tabulate and compare the results. 

Question. — How much more reserve plant food is there as 
N, P2O5, and K 2 in heavy- than in light-weight seeds ? 

Movement of Plant Juices 

339. Joint Action of Chemical and Physical Agents. 

— The compounds produced in the leaves of plants are 
transported and stored in other parts, as the seeds or 
roots. This is brought about by the joint action of 
physical and chemical agents. This action can best be 
understood by first considering some of the properties 
of plant tissues, as porosity, capillarity, and osmosis. 

340. Porosity of Tissues is a property common to all 
forms of matter, and one possessed particularly by vege- 
table substances. The living plant not only permits 
the passage of water through its tissues, but absorbs it 
until the pores are filled. Animal and vegetable tissues 
have power to take up and tenaciously hold water within 
their fibers. This is, in part, due to capillary action. 
Capillarity, assisted by evaporation, explains only in 
part, however, the movement of the plant juices. Com- 
pounds formed within the leaf must be transported in an 
opposite direction to that of sap in moving from the 
roots to the leaves. This movement is effected by osmosis 
and chemical reaction within the cells. 

341. Osmosis. — When a bottle filled with a solution of 
salt colored with litmus is placed in a large vessel of 
water, the bottle will discharge its contents into the 



230 AGRICULTURAL CHEMISTRY 

larger body of water and the movement of the solutions 
can be followed with the eye. With sugar and salt 
solutions separated by a membrane, there is a gradual 
interchange of the two solutions ; some of the sugar 
finds its way into the salt solution, and some of the salt 
into the sugar solution. There is a tendency for an 
equilibrium to be established. This action or interchange 
is still further increased when the solutions are of different 
densities and when chemical action is taking place on 
both sides of the membrane. Such action occurs in plant 
tissues, which are composed of a large number of small 
cells, the walls of which serve in part as membranes, 
and offer but little resistance to diffusion. The cells are 
filled with sap, which is acid in nature and contains 
numerous solid substances in solution. Between the 
cells are intercellular spaces filled with sap of different 
density from that within the cells and charged with other 
kinds of matter. Here, then, are nearly the same con- 
ditions as those of the salt and sugar solutions, and the 
result, osmosis, is the same in each case. Within the 
cell walls active chemical changes are taking place which 
aid in this interchange. It cannot be said that there is 
a constant flow of sap in any one direction, as blood 
flows in the animal body. The movement of the plant 
juices is considered as due to (1) capillary action, aided 
by evaporation, which disturbs the equilibrium of the 
plant juices, together with (2) osmosis, aided by chemical 
action within the cells. These factors are, to a certain 
extent, mutually dependent upon each other. By their 
joint action, and the chemical changes within the plant, 
the water from the soil is taken into the plant through 
the roots with the mineral matter in solution, which 
serves as food, and finds its way all through the plant, 



CHEMISTRY OF PLANT GROWTH 23 1 

finally returning to the roots charged with the material 
that can be made only in the leaf and by the aid of light 
and sunshine. 

Chlorophyll and Protoplasm 

342. Chemical Action in Leaves of Plants. — All of the 

organic compounds of plants are produced within the 
cells of the leaves. The mineral food and nitrogen taken 
from the soil and the carbon dioxid from the air are 
chemically united in the cells of the leaves to form the 
various non-nitrogenous and nitrogenous compounds of 
plants. Chlorophyll and protoplasm are the two sub- 
stances which take the most active part in the production 
of the organic compounds. 

343. Chlorophyll is the name applied to the material 
that imparts the green color to plants. It is not a simple 
compound, but is composed of a number of closely related 
organic bodies. Chlorophyll contains both organic and 
mineral matter. Chlorophyllan is one of the compounds 
obtained from chlorophyll. Iron, phosphorus, and magne- 
sium are among the more important mineral elements 
necessary for the functional activity of chlorophyll. This 
mineral matter is in combination with the organic com- 
pounds which form a part of the chlorophyll grain. Chlo- 
rophyll is contained in the active living cells of plants, but 
makes up only a small part of the contents of the cell. 

344. Protoplasm. — The chlorophyll body is suspended 
in a gelatinous, colorless liquid called protoplasm, which is 
composed mostly of proteids and albuminoids. It is the 
living substance of the plant organism, and is the part 
which gives life and activity. In chemical composition, 
it is exceedingly complex, and is composed of a number 
of proteids, albuminoids, and other organic compounds. 



232 AGRICULTURAL CHEMISTRY 

Protoplasm, aided by chlorophyll, has the power of 
combining the food elements and producing all of the 
organic compounds of the plant. Protoplasm is the 
living part of both plant and animal cells. 

345. Production of Chlorophyll. — When the plant cell 
is formed, the protoplasm contains no green grains. 
Small, colorless grains first appear, and then the greening of 
these grains takes place. The chlorophyll body may make 
its appearance in the absence of light, but the last stage 
of its development can take place only under the influence 
of light and at a higher temperature than is required for 
the first stage of the process. In cool spring weather there 
is plant growth, but the vegetation looks yellow because 
there is not sufficient heat to complete the second part 
of the process of chlorophyll development. Chlorophyll 
is destroyed by intense light as well as by absence of light. 
It is soluble in ether and alcohol and is one of the constit- 
uents of ether extract. The green color is easily de- 
stroyed, but the chlorophyll body is quite stable and 
resists the action of dilute acids and alkalies. Chlorophyll 
loses its activity and undergoes a decided change in 
composition as the plant matures. Some of the elements 
of which it is composed, as nitrogen and phosphorus, 
are used for seed formation. At the time of the most 
color in plants, there is the greatest cell activity and the 
largest amount of plant tissue is being produced. When 
a plant ripens, the decline of activity of the cells may 
be observed by the change in the color of the plant. With 
corn, for example, the lower joints of the stalk turn 
yellow first, indicating that growth and activity have 
ceased in those parts. Then the upper leaves become 
yellow, and finally the husk becomes yellow and inactive. 
Chlorophyll is one of the principal agents which takes 



CHEMISTRY OF PLANT GROWTH 233 

an active part in plant growth, and whenever chlorophyll 
is destroyed, plant growth is checked. 

Experiment 68. — Extracting chlorophyll from leaves. Place in 
a test tube 0.5 gram of dry, green leaves. Add 10 cc. alcohol, 
shake vigorously and, after the alcohol is colored green, filter off the 
solution, and evaporate to dryness at a low temperature on the 
water bath. 

Questions. — (1) Describe the appearance of the chlorophyll resi- 
due. (2) What is chlorophyll ? (3) Of what is it composed ? 
(4) What other solvents could be used in place of alcohol ? 

346. Function of Chlorophyll. — The chief function of 
chlorophyll, aided by protoplasm, is the production of 
starch and other organic compounds in the cells of plant 
leaves. Chlorophyll alone cannot perform this function, 
but must be associated with, and aided by, protoplasm. 
Minute starch grains are sometimes found within the 
chlorophyll grains. The growth of starch within the 
chlorophyll body can be observed with the microscope. 
No other compound has been found so organically con- 
nected with the chlorophyll grains as starch. If a plant 
is placed in darkness, both the starch and the coloring 
matter in the plant cells disappear. The plant cell is the 
chemical laboratory in which the various organic com- 
pounds, as starch, sugar, and proteids, are elaborated. 
From the cells in the leaves, they are transported to other 
parts of the plant, as the seeds, roots, or tubers, where they 
are stored up and serve as reserve food. 

347. Production of Organic Matter. — By the joint 
action of the protoplasm and chlorophyll within the plant 
cells, starch and all other organic compounds are pro- 
duced from the carbon dioxid of the air and from the 
water, mineral matter, and nitrogen of the soil. All of 
the carbohydrates can be produced from starch, as was 



234 AGRICULTURAL CHEMISTRY 

stated in Section 289, which discusses the general rela- 
tionship existing between the various non-nitrogenous 
compounds. Fat, as well as other non-nitrogenous com- 
pounds, is produced from starch. Proteids are produced 
from amides. By a succession of chemical changes, the 
amide molecule takes on fatty acid and carbohydrate 
radicals, and complex proteids are the result. All of 
these chemical changes take place within the plant cell ; 
and for the production of the various compounds which 
constitute the dry matter of plants there are required 
the essential mineral elements, nitrogen in combination, 
carbon dioxid, and water. 



CHAPTER XXVI 

Composition of Plants at Different Stages of 

Growth 

348. Composition and Stage of Growth. — Plants do 
not have the same chemical composition at different 
stages of growth. Chlorophyll and protoplasm are most 
active in the early stages and produce the nitrogenous 
compounds more rapidly than the non-nitrogenous. 
The later stages of plant growth are utilized mainly for 
the production of carbohydrates and for the various 
chemical and physical changes incident to ripening and 
the transfer of the organic compounds from the leaves 
to the seeds. Plants have a different food value at their 
various stages of growth as well as a different chemical 
composition. 

349. Assimilation of Mineral Food by the Wheat Plant. 

— The elements of plant food utilized by spring wheat 
are assimilated quite rapidly in the early stages of growth. 
The mineral matter essential for the production of the 
organic compounds is taken from the soil in advance of 
their formation. Before the crop has completed the 
first half of its growth, over 75 per cent of the total mineral 
matter needed for the ripened grain has been absorbed. 
Of the mineral elements, phosphorus, potassium, and 
calcium are assimilated most rapidly. 

350. Assimilation of Nitrogen by the Wheat Plant. 

— The nitrogen utilized by a spring wheat crop is taken 
from the soil in advance of the mineral matter. Nitrogen 
is assimilated more rapidly than any other of the elements 

235 



236 AGRICULTURAL CHEMISTRY 

which form a part of the organic compounds of plants. 
Under normal conditions about 85 per cent of the total 
nitrogen required has been taken from the soil when the 
wheat plant has completed half its growth. This is 
one reason why nitrogen and the essential ash elements 
should be present in the soil in available and liberal 
amounts for a wheat crop. With the maximum of any 
element or compound considered as 100, the correspond- 
ing amounts present during the different stages of growth 
of the wheat plant are as follows : 

Wheat, 50 Wheat, 65 Wheat, 80 Wheat, 

days, before days, headed days, milk harvest 
heading out. out. state. time. 

Total dry matter 46 59 95 100 

Organic matter 44 57 90 100 

Total nitrogen 86 89 96 100 

Potassium oxid 45 88 100 94 

Calcium oxid 67 91 100 96 

Magnesium oxid 57 68 99 100 

Phosphoric anhydrid. ... 80 83 98 100 

351. Clover; Rapidity of Growth. — The same general 
order of changes occurs at the different stages of the 
growth of clover as of wheat, but the two plants are so 
unlike, clover being a biennial and a legume, and wheat 
an annual and a grain, that the rapidity of growth and 
formation of organic compounds in the two plants are 
naturally dissimilar. The largest portion of the dry 
matter in clover is produced between early and full bloom. 
During this period, too, about 60 per cent of the organic 
compounds are formed. As in the case of wheat, the 
nitrogenous compounds developed more rapidly and in 
advance of the non-nitrogenous. At the time of early 
bloom, about 37 per cent of the total nitrogenous com- 
pounds have been formed, but the crop at this stage has 



PLANT GROWTH AT DIFFERENT STAGES 



237 



only 31 per cent of the total organic compounds. When 
clover is very young, before the flower head is visible, it 
has only about 10 per cent of the total organic compounds, 
but this organic matter is rich in nitrogen as it contains 
about 15 per cent of the total amount assimilated by the 
crop ; however, a large share of this nitrogen is in the 
form of amide compounds. Analyses of the leaves and 
stems, at different stages of growth, show that the leaves 
of young clover contain about 2.5 times as much ni- 
trogenous matter as the stems, while at maturity there is 
less than twice as much. At full bloom, the largest 
amount of nitrogenous matter is present, and it is then in 
the form of proteids to the extent of about 88 per cent. 
In the last stages of growth there is a noticeable increase 
in the content of crude fiber. The differences in compo- 
sition and feeding value between clover, cut and cured in 
full bloom, and at maturity, are as follows : 

Clover at Full Bloom. 



2. 



The crop contains less fiber 
than when mature. 

The crop contains its maxi- 
mum amount of proteids. 

A smaller yield per acre is se- 
cured than at maturity, 
but the crop is more con- 
centrated in protein. 

Clover when Ripe. 

The crop contains a larger 4. Some of 
amount of fiber. 

The crop contains a smaller 
per cent of protein than 
when in full bloom. 

A larger yield per acre is se- 
cured, and the crop is more 
concentrated in carbohy- 
drates. 



The nutrients are more evenly 
distributed. 

The crop contains its maxi- 
mum amount of essential 
oils, which impart palata- 
bility. 

The nutrients are more di- 
gestible. 

the nutrients are 
transferred to the seeds, 
leaving less in the stems. 

At maturity, there are less 
of the essential oils than at 
any other period. 

At maturity, the crop is less 
digestible than at full bloom. 



238 AGRICULTURAL CHEMISTRY 

Composition of Clover at Different Stages of Growth. 

Flower head Early Full End of 

invisible. bloom. bloom. flowering. Ripe. 

Per cent. Per cent. Per cent. Per cent. Per cent. 

Water 86.00 85.59 74.96 71.65 33.47 

Dry matter 14.00 14-41 25.04 28.35 66.53 

Composition of the Dry Matter. 

Ash 10.57 10.22 6.85 7.02 6.21 

Ether extract 5.35 4.70 5.73 4.26 3.92 

Crude protein. . . . 23.61 17-19 14.81 14.40 14.06 

Crude fiber J3-37 20.08 24.62 25.28 26.60 

Nitrogen-free ex- 
tract 47-io 47-8i 47-99 49-°4 49.21 

Composition of the Dry Matter of the Leaves and Stems. 

Flower head invisible. Early bloom. Third period. 

Leaves. Stems. Leaves. Stems. Leaves. Stems. 

Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. 

Ash 10.02 11.02 10.07 11 -3o 9.19 4.87 

Crude protein .. . 30.68 13-44 27.38 11.25 J 9-37 11.26 
Crude fiber 10.48 18.46 10.51 26.32 15.36 35.27 

When the largest amount of any compound in the crop 
is considered as 100, the percentage amounts at the 
different periods of growth are as follows : 

Flower head Early Full End of 

invisible. bloom. bloom, flowering. Ripe. 
Per cent. Per cent. Per cent. Per cent. Per cent. 

Dry matter 9 31 97 100 97 

Total ash 14 46 98 100 95 

Total nitrogen 15 37 100 96 94 

Proteid nitrogen 67 70 88 85 83 

Fiber 5 24 92 96 100 

Potassium oxid 15 50 100 94 86 

Calcium oxid 15 37 97 100 97 

Magnesium oxid 8 35 100 92 91 

Phosphoric anhydrid 14 34 98 100 98 

(These tables are from Minn. Expt. Sta. Bull. 34.) 



PLANT GROWTH AT DIFFERENT STAGES 230 

352. Flax; Rapidity of Growth. — The flax plant has a 

short growing period, about seventy days, and the plant 

food is assimilated at a rapid rate. Before the time of 

bloom, the nitrogen and mineral matters have been 

absorbed in quite large amounts. When 40 per cent of 

"the organic matter has been produced, the flax plant 

contains 55 and 60 per cent, respectively, of its total 

nitrogen and mineral matter. When the flax is in full 

bloom, 75 per cent of the organic compounds have been 

formed. After seed formation begins, there is no nitrogen 

or mineral matter taken from the soil. Flax is very 

rich in nitrogen, containing even more than clover. This 

is one of the few crops in which the ash in the seed exceeds 

that in the straw; the seed contains about 3.75 per cent 

ash, while the straw contains less than 3 per cent. The 

oil in the seed is derived mainly from starch in the later 

stages of growth. Between full bloom and maturity, 

less than 25 per cent organic matter is produced. The 

rate of formation of the organic matter and assimilation 

of the elements from the soil are given in the following 

table : 

Before In full Seeds well 

bloom. bloom. formed. Ripe. 

Per cent. Per cent. Per cent. Per cent. 

Total organic matter 4 o ?5 95 

Total nitrogen 55 8o 1QQ 

Calcium oxid 32 ^ gg iqq 

Potassium oxid 55 go 1QQ 

Phosphoric anhydrul 35 ?0 g8 

(Minn. Expt. Sta. Bull. 47.) 

Maize (Corn) 

353- Importance. — Indian corn or maize is grown 
over a wide range of territory, and is used alike for animal 



24O AGRICULTURAL CHEMISTRY 

and human food, and since as an animal food it may 
serve either as grain or forage, a knowledge of the chemical 
changes which takes place during its growth, and the 
composition of the plant at maturity, will enable the 
student to utilize this crop more economically in the feed- 
ing of farm animals. The facts relating to the composi- 
tion of corn at different stages of growth and the analyses 
given in this chapter, are taken largely from Bulletin 
No. 9, Mo. Agr. Expt. Station. 

354. Roots. — The function of the roots is to collect, 
assimilate, and transport to other parts of the corn plant 
the nitrogen and mineral food from the soil. In mature 
corn, a small amount of the essential elements of plant 
food is in the roots, only sufficient for the structure of 
the root tissues. During growth, there is always some 
being transported to the parts above ground. At 
maturity, the dry matter in the roots constitutes about 
5 per cent of the dry matter of the plant. The roots 
contain the most fiber and least fat of any part of the 
plant. Of the ash elements, soda is present in greater 
amounts than in the parts above the ground. In the 
early stages of growth, the roots are very rich in iron, 
which decreases as the plant matures, because of its 
being given over to other parts. The nitrogen in the 
roots never, at any stage of growth, exceeds 1.25 per 
cent of the dry matter; it is transported to the parts 
above ground more rapidly than any other element. 
During the last fifteen days of growth, there is but little 
mineral food, except magnesia, taken up, and there is a 
loss of about 12 per cent of potash from the roots, which 
indicates that the retrograde movement of potash at 
maturity may extend from the roots back to the soil. In 
the later stages of growth, there is a great influx of mag- 



PLANT GROWTH AT DIFFERENT STAGES 241 

nesia. Silica and the non-essential ash elements make 
up the larger portion of the ash elements in the mature 
plant. 

355. Stalk. — The stalk undergoes during growth a 
decided change in composition ; there is a gradual in- 
crease in the content of fiber and a decrease in proteids. 
The outside of the stalk is different in chemical compo- 
sition from the pith. The highest per cent of dry matter 
is found in the stalks from two to three weeks before 
maturity. As the plant matures, the proteid and circu- 
latory carbohydrates are transferred to the seed. When 
mature, both pith and stalk have a low content of protein, 
fat, and digestible carbohydrate, and hence a low feeding 
value. The pith is somewhat richer in nitrogenous 
matter than the stalk. The ash of the stalk is character- 
istically rich in silica. 

356. Leaves. — Since all the chemical compounds of 
the plant are first produced in the leaves, and then trans- 
ported to other parts, it follows that the leaves at different 
stages of growth have a variable composition. The 
cells of the young leaves contain more protoplasm than 
mature leaves, the largest amount of nitrogenous matter 
being present there in the early stages of growth. As the 
plant matures, this nitrogenous matter is given up for the 
formation of other parts, and there is then a decline in the 
nitrogen of the leaves. The largest amount of dry matter 
in the leaves is about six weeks before maturity. The 
plant as a whole, however, increases rapidly in dry matter 
after this time, although no additional organic matter ac- 
cumulates in the leaves, but it is used for seed formation. 
As the plant matures, the ash in the stems declines, while 
that in the leaves steadily increases, due to silica, which 
is deposited there as inert material. Also the phos- 



242 AGRICULTURAL CHEMISTRY 

phorus content of the leaves declines, at this time, the 
phosphorus, like the nitrogen, being stored in the seeds. 
The largest amount of potash in the leaves is at the time 
of the most dry matter, about six weeks before maturity. 
Next to the seed, the leaves contain the most protein, 
fat, and digestible carbohydrates of any part of the plant. 
When green, the leaves have a higher nitrogen content 
than when yellow. The feeding value of corn fodder 
depends to a great extent upon the condition of the leaves. 

357. Tassel. — The tassel has some of the chemical 
characteristics of the seed ; it is concentrated in nitrogen, 
has less fiber, and an ash rich in phosphates. The flower 
stalks and anthers yield an ash in composition like that of 
the stems, while the ash of the pollen is nearly identical 
with that of the matured grain. The pollen is par- 
ticularly rich in nitrogen. One of the claims made for 
detasseling corn is to prevent loss of nitrogen and phos- 
phoric acid through the pollen. It is estimated that the 
nitrogen removed in the pollen amounts to from 5 to 
10 pounds per acre. Both the fresh and the dried silk 
(stigmas) show a decline in nitrogen and phosphoric acid 
after fertilization. 

358. Husk. — The husk when first formed has all of the 
materials for the development of the seed, and its compo- 
sition at different stages of growth shows a gradual transfer 
of its constituents to the ripening grain. When fully 
mature, the husks are much poorer in ash and nitrogen 
than the leaves or stems, but not so poor as the cob. 
The cob remains functionally active longer than any other 
part of the plant, and is composed largely of cellulose and 
pentose compounds, with but little protein or fat. 

359. Ripening Period. — The corn plant, at first, 
absorbs its mineral food and nitrogen at a very rapid 



PLANT GROWTH AT DIFFERENT STAGES 243 

rate. In fact, there is little mineral matter or nitrogen 
assimilated during the last few weeks of growth. The 
last stage of development is a period of rearrangement and 
transportation of the compounds from the leaves to the 
seed. The composition of the different parts of the corn 
plant when mature and of the ash is given in the following 
table : 



244 



AGRICULTURAL CHEMISTRY 





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CHAPTER XXVII 

Factors which influence the Composition and 
Feeding Value of Crops 

The main factors which- influence the composition and 
feeding value of crops are : (i) seed, (2) soil, (3) climate, 
(4) stage of maturity, (5) method of preparation as food, 
and (6) combination with other foods. 

360. Seed. — The composition and individuality of the 
seed influence the composition and feeding value of the 
forage crop. Heavy-weight seeds are usually more 
mature and contain a larger amount of reserve plant 
food than those of light weight (see Section 338). Experi- 
ments by Hellreigel show that the heavier the seed, the 
more vigorous the young plant. When there was not 
an overabundance of plant food in the soil, the difference 
in vigor of plants was discernible even up to the time of 
harvest. Experiments show that by careful selection of 
seed corn, the percentage amount of nitrogenous matter in 
the grain may be increased from 0.5 to 1.25 per cent. Not 
all of the cereals respond as does corn to the influence of seed 
selection to produce variations in chemical composition. 

The care and storage which the seed receives prior to 
planting also influence its vitality. When seed corn is 
stored in a damp or poorly ventilated place, the excessive 
amount of moisture results in injuring the vigor of the germ. 
Seed wheat is often injured by being stored in elevators 
where bin-burning caused by fermentation takes place. 
Sound, heavy seeds of full maturity always give the best crop 
returns. Forage crops are more susceptible to seed influ- 

245 



246 AGRICULTURAL CHEMISTRY 

ences than are grain crops, because the leaves and stems of 
plants are less constant in composition than is the seed. 

361. Soil. — The condition of the soil as to available 
plant food has a material influence upon composition, 
and in promoting a balanced crop growth. Experiments 
conducted at the Connecticut Experiment Station (Storr's 
Annual Reports, 1898, 1899) show that fodder crops 
grown with a liberal supply of nitrogen have a tendency 
to contain more of the nitrogenous compounds than 
similar crops grown with a scant supply. The nitrogen 
and available mineral matter increase the activity of 
the protoplasm and chlorophyll in the production of all 
of the organic compounds. With a larger amount of 
available plant food, particularly nitrogen, a larger amount 
of foliage is produced. All foliage crops grown upon 
rich soils have larger leaves and a higher nitrogen content 
than those grown on poor soils. 

The condition of the soil influences the composition of 
leaves and stems to a greater extent than it does the com- 
position and character of the seeds because they are more 
constant in composition. The selection of seed corn has 
a greater influence upon the composition and feeding 
value of corn fodder than it has upon the grain. Fodder 
crops, produced upon fertile soils and under favorable 
climatic conditions, have the highest feeding value. The 
condition of the soil, as to acidity or alkalinity, also 
influences the character and composition of crops. Crops 
produced upon acid soils have a different appearance from 
those grown upon mildly alkaline soils. An unbalanced 
condition of plant food in the soil produces an unbalanced 
crop growth. It is not possible, however, by the use of 
manures or the selection of seeds, to entirely change the 
composition of crops. In the extensive experiments by 



FEEDING VALUE OF CROPS 247 

Lawes and Gilbert (Rothamsted Memoirs, Vol. Ill), the 
continued use of nitrogen and mineral manures for a 
period of twenty years showed no material increase in the 
amount of nitrogenous matter in the wheat. In similar 
experiments with potatoes, in which nitrogenous manures 
alone were used, there was an increase of 0.05 per cent 
of nitrogenous matter. The sugar-beet has been greatly 
changed in composition by cultivation. The content 
of sugar has been increased from 8 to 16 per cent. Wheat 
and other grains show material differences in weight and 
composition when grown upon different types of soil. 
Experiments have been made where wheat grown from 
one lot of seed under different climatic and soil conditions 
showed a difference of 18 bushels per acre in yield, and 
8 pounds per bushel in weight (Minn. Expt. Sta. Bull. 
No. 2$). Forage crops produced upon soils of high 
fertility have a higher feeding value than crops grown 
upon poor soils. At the Minnesota Experiment Station, 
timothy and corn fodder grown on land that had been 
manured and rotated, and similar crops grown on unma- 
nured land, showed the following amounts of protein : 

Timothy hay grown on Corn fodder grown on 

manured unmanured manured unmanured 

land. land. land. land. 

Per cent. Per cent. Per cent. Per cent. 

Crude protein (dry 
matter basis) .. . 8.75 6.45 8.85 6.32 

362. Climate. — In the early stages of plant growth, the 
nitrogenous compounds are produced more abundantly 
than are the non-nitrogenous (Section 351). If the 
growing season is in any way cut short, the crop has a 
slightly larger amount of nitrogenous matter than if 
normal conditions prevail. Any shortening of the grow- 
ing period or forcing of the crop to maturity lessens the 



248 AGRICULTURAL CHEMISTRY 

per cent of dry matter, increases the nitrogenous com- 
pounds, and decreases the carbohydrates. The composi- 
tion of grains is influenced by climatic conditions, particu- 
larly at the time of seed formation, when growth is often 
checked before all of the compounds have been trans- 
ferred from the leaves to the seeds ; shrunken or immature 
grain is the result. Such grain contains less starch and 
more nitrogenous compounds than that which has fully 
matured. Experiments with potatoes by Lawes and 
Gilbert show that they too are, to a slight extent, influ- 
enced in composition and starch content by climatic 
conditions ; the longer the growing period, the larger the 
amount of starch. A short and favorable growing season, 
together with a fertile soil, has the tendency to produce 
crops of high nitrogen content. 

363. Stage of Maturity. — Since all crops at first 
produce nitrogenous compounds in larger amounts than 
at later stages, it follows that early cut crops contain 
proportionally more nitrogen than those cut later. This 
increase in nitrogenous matter is, however, at the expense 
of the total dry matter in the crop. If crops are cut too 
early, that is, before early bloom, too much of the nitro- 
gen is in the form of amides, some of which are changed 
to proteids at a later stage. Early cutting results in 
securing a smaller yield per acre of dry matter, more 
concentrated in nitrogenous compounds. When fodder 
crops are cut at early or full bloom, the nutrients are more 
evenly distributed than at maturity, when some of the 
proteids and carbohydrates have been transferred from 
the leaves to the seeds, leaving stems and leaves with a 
larger amount of fiber and less protein. The composition 
and comparative feeding value of clover cut at different 
stages of growth are given in Section 351. 



FEEDING VALUE OF CROPS 249 

364. Method of Preparation as Food. — The method of 
curing and preparing fodder affects its food value. Over- 
drying causes mechanical loss of leaves, which gives the 
fodder different composition and feeding value than 
when the leaves are all secured. Bleaching results in 
partial destruction of the chlorophyll and a loss of the 
essential oils that impart palatability. Other chemical 
changes which have a tendency to make the fodder less 
digestible also take place. Mechanical loss of leaves 
and exposure to leaching rains result in a loss of nutritive 
value. The materials extracted are the most soluble 
and digestible. A heavy, leaching rain may extract 
10 per cent or more of the nutrients, making the leached 
fodder less digestible and less palatable. 

The method of storing and the mechanical condition of 
a fodder also influence, to a limited extent, the avail- 
ability of the nutrients. The influence which the com- 
bination of fodders has upon digestibility and food value 
is discussed in Chapter XXXV. 

365. Improving the Feeding Value of Forage Crops. — 
The main factors, as seed, fertility of soil, stage of 
maturity, and care which the fodder receives, are all 
under the control of the farmer, climate being the only 
factor that is not directly controllable. Lack of moisture 
in dry seasons can, however, in part, be overcome by shal- 
low cultivation. By careful selection of seed, conserving 
the fertility of the soil, and suitable methods of cultivation 
and storage, it is possible not only to increase the yield 
but also to change the chemical composition and feeding 
value of forage crops. As yet, experiments have not 
demonstrated the extent to which all crops are susceptible 
to these influences. 



CHAPTER XXVIII 



Composition of Coarse Fodders 

366. The Term Coarse Fodders is applied to animal 
foods which usually contain large amounts of crude fiber, 
and, while bulky in nature, are essential foods, many of 
them having high nutritive value. A coarse fodder 
may be either green or field-cured ; pasture grass, timothy 
hay, and corn fodder are all examples of coarse fodders. 
The proteid content ranges from 4 per cent and less, in 
straw, to 12 per cent and more, in clover and legumes. 
Coarse fodders may be classed as : 

Low protein content 2 to 5 per cent. 
Medium protein content 5 to 9 per cent. 
High protein content 9 per cent and upwards. 

367. Straw. — The straw from wheat, oats, barley, and 
rye contains from 36 to 38 per cent of crude fiber, and 

less than 4 per cent of 



crude protein, oat 
straw being the rich- 
est in protein. The 
amount of fat in straw 
is small, rarely exceed- 
ing 1.5 per cent. The 
water content is 
usually from 6 to 9 per 



ETHtR EXT 




WHEAT STRAW 

Fig. 84. — Composition of a bale of 



wheat straw. 

cent. The pentose compounds make up a large portion of 
the nitrogen-free extract. Straw is a food poor in protein, 
fat, and digestible carbohydrates, and contains a high per 

250 



COMPOSITION OF COARSE FODDERS 



251 



cent of ligno-cellulose, pentose, and ash materials. Straw- 
may produce some heat in a ration, but for the production 
of muscle or the repair of proteid matter, it occupies 
about the lowest place in the list of animal foods. The 
various factors which influence the composition of plants 
(see Chapter XXVII) affect the composition of the straw. 
That from immature grain has higher feeding value than 
from grain fully ripened, because in the unripe state less 
of the nutrients has been removed for seed formation. 
The greener the straw, the higher its food value. 

368. Timothy Hay. — Timothy hay has more protein, 
but in other respects the same general characteristics as 
straw. The per cent of fiber usually ranges from 28 to 
32 per cent or more, which is from 6 to 10 per cent less 
than in straw. The 
crude protein ranges 
from 5.5 to 9 per cent 
according to the condi- 
tions under which the 
crop was grown. Aver- 
age timothy hay con- 
tains 7.5 percent, which 
is about twice as much 
as found in straw. The 
amount of ether extract is about 2.25 per cent, of which 
a large portion is non-fatty material. As in the case 
of straw, the nitrogen-free extract of timothy consists 
largely of pentose bodies ; there is also a small amount 
of soluble carbohydrates. While timothy hay is not 
rich in protein, it is a valuable fodder, particularly when 
one of fair energy-producing power is desired, as for feed- 
ing work horses. Mixed timothy and clover hay have 
more protein than timothy alone. 




timothyha? 
Fig. 85. - 



Composition of a bale of 
timothy hay. 



252 AGRICULTURAL CHEMISTRY 

369. Hay Similar to Timothy. — Millet, blue grass 
hay, and the numerous varieties of native prairie hay have 
about the same general composition and feeding value as 
timothy hay. Each, however, differs from timothy to a 
slight extent, both in chemical composition and structure 
of parts, some being preferable to others for feeding 
certain kinds of animals. These hays are classed as 
coarse fodders containing low to medium amounts of 
crude protein, and they vary in protein content from 6 to 
9 per cent according to the conditions under which they 
are grown and other factors which affect their composition. 

370. Oat Hay. — When oats are cut at the heading-out 
stage and cured as hay, they make a valuable fodder 
which compares favorably with the best grades of timothy 
hay, and usually contains slightly more protein than 
timothy, or hays of similar character. Oat hay should be 
cured for fodder while the nutrients are evenly distributed, 
and before they are transported and stored up in the grain. 

371. Hay Similar to Oat Hay. — Wheat and other 
cereals, cut at the right stage, have a similar compo- 
sition and feeding value to oat hay. In localities where 
the climatic conditions do not admit of the growth of 
perennial grasses, these forage crops are grown. 

372. Bromus Inermis varies in composition and feed- 
ing value according to the stage when cut. When over- 
ripe, its protein content is between that of straw and 
timothy hay. If cut or pastured while young, it has a 
high feeding value. In this crop, the non-nitrogenous 
compounds, particularly fiber, are formed at a rapid 
rate in the last stages of growth. 

373. Clover Hay is characteristically rich in crude 
protein, containing nearly twice as much as poor grades of 
timothy. There is less crude fiber and more ether extract. 



COMPOSITION OF COARSE FODDERS 



253 




f ETHER EXT 



CLOVER HAY 

Fig. 86. — Composition of a bale of clover hay. 



The large amount of crude protein and other nutrients 
makes it one of the most valuable fodders that can be 
produced for growing, fattening, or milk-giving animals. 
There is no coarse fodder, except alfalfa, that has so high 
a protein content as clover when grown and cured under 
the best conditions. 
Clover ash is of differ- ^£s£f: 
ent composition from 
timothy ash. It con- 
tains a small amount 
of silica and a large 
amount of lime, while 
timothy ash contains 
more silica and less 
lime. The nitrogen-free extract of clover is largely pentose 
materials. The composition and comparative feeding 
value of early- and late-cut clover are given in Section 351. 
In curing clover hay, it should be the aim to prevent 
mechanical loss of leaves during handling of the crop. 
When clover hay is fed to stock, less grain and milled 
products are required than when hays of lower crude 
protein content are used. There are a number of varieties 
of clover ; alsike, crimson, scarlet, and white clovers, all 
having about the same general composition. Each, how- 
ever, has characteristic habits of growth which make it 
peculiarly adapted to certain soil and climatic conditions. 
374. Alfalfa and Fodders Similar to Clover. — Alfalfa 
has somewhat the general composition and feeding value 
of clover, but its physical composition, as density of 
tissue and proportion of leaves to stems, is different, and 
it can be grown under more adverse climatic conditions. 
All members of the leguminous or pulse family, to which 
clover, alfalfa, peas, cowpeas, and vetch belong, are 



2 54 AGRICULTURAL CHEMISTRY 

characteristically rich in protein, and are among the most 
valuable forage crops. The discovery, by Hellreigel, of 
the unique value of clover and other legumes in assimi- 
lating the free nitrogen of the air by means of the action 
of microorganisms associated with the roots of these 
plants, and of the use of leguminous crops in increasing 
the supply of nitrogen in the soil, is one of the greatest 
achievements of agricultural chemistry. In Plate III, 
the arrow indicates one of the nodules containing the 
nitrogen-assimilating organisms. 

375. Rape. — The rape plant contains nearly as much 
crude protein as clover hay. Because of the presence of 
certain volatile oils, it cannot be fed to milk cows without 
imparting an unpleasant taste to the milk. Rape, how- 
ever, is valuable for the feeding of all growing and fattening 
animals. 

376. Pasture Grass. — In studying the composition 
of plants at different stages of growth, it was stated that 
the nitrogenous compounds are produced more rapidly 
than the non-nitrogenous (Section 351). The dry matter 
of pasture grass is more nitrogenous in character than 
that of the matured crop. The dry matter of all kinds 
of pasture grass is rich in crude protein ; the various 
nutrients, however, range between wide limits, according 
to the species of grass, and the conditions affecting its 
growth. When a piece of land is grazed, a smaller amount 
of total nutrients is secured than if a forage crop were 
harvested and fed. Pasturing is similar in results to a 
series of early cuttings, before bloom, rather than one 
later cutting, as in harvesting a crop. 

377. Corn Fodder and Stover. — By corn fodder is 
meant the entire corn plant with or without ears, accord- 
ing to the conditions under which it has been grown, 




Plate III. — Clover Roots. 



COMPOSITION OF COARSE FODDERS 



255 




ETHER EXT 



while corn stover is the plant after the grain has been 

removed. Corn fodder is one of the most valuable, 

palatable, and largest yielding crops that can be produced. 

When sown so that no ears, or very 

small ones, are developed, the leaves 

and stalks contain all of the nutrients 

which would otherwise be stored in the 

seed. When grown under favorable 

conditions, corn fodder contains about 

the same per cent of crude protein as 

timothy hay, and is equal in value to 

the best quality. When field-cured, it 

contains from 15 to 30 per cent of water, 

from 12 to 25 per cent of crude fiber, 

and from 2.5 to 4 per cent of ash. In 

the study of the composition of the corn CORN fodder 

plant (Chapter XXVI), the Content of Fig. 87. — Composition 

crude protein and other nutrients in ? f * shock of corn 

1 . . fodder. 

the various parts of the plant was 
considered. In growing corn fodder, it should be the 
aim to produce a large number of medium-sized plants 
with large leaves, small or no ears, and small stalks. Thus 
the largest amount of nutrients most evenly distributed, 
palatable, and digestible are secured. Corn stover has 
more of the characteristics of a straw crop, and is not so 
valuable as corn fodder. When ears are produced, the 
protein is stored in them, and hence less is found in stalks 
and leaves. The physical condition and chemical form of 
the cellulose, as hydrated or lignose, also influence the 
feeding value of corn fodder and corn stover. Corn 
fodder can be fed to all kinds of farm animals, and is one 
of the cheapest forage crops. It is valuable alike for 
horses, sheep, and dairy and beef cattle. 



256 AGRICULTURAL CHEMISTRY 

378. Silage. — In preparing silage the green material 
is placed in a nearly air-tight compartment. Corn, 
clover, or any green crop may be cured as silage. Corn, 
however, is the crop most generally given this treatment, 
and unless otherwise designated, silage usually has refer- 
ence to corn fodder prepared in this way. 

The chemical changes that take place in the silo are 
caused mainly by ferments. Carbon dioxid, hydro- 
carbons, and ammonia in small amounts are among the 
volatile products formed. There is always a loss of dry 
matter in curing silage. This is greatest in the top layer 
and least in the bottom. The losses in the different 
sections of a silo may range from 5 to 25 per cent. In a 
large silo the losses are less than in a small one, and they 
need not exceed 5 per cent of the dry matter. 

The average of a number of trials shows that when corn 
fodder is prepared as silage, there is a loss of from 5 to 25 per 
cent of dry matter, of which a proportional amount is pro- 
tein. Including mechanical losses, there is nearly the same 
in field curing of corn fodder as in its preparation as silage. 

The temperature of the silage, when undergoing fermen- 
tation, ranges from 35 to 75 C. The lower temperatures 
generally produce poor silage, while the higher yield a 
better quality. In order to make sweet silage, the condi- 
tions should be such that the temperature during fermen- 
tation is kept above 43 ° C, so as to render the acid spore 
that produces the sour silage less active and allow other 
ferments to act. No appreciable amount of alcoholic 
fermentation takes place in the silo. The corn for silage 
should be cut green rather than overripe, and should be 
evenly packed in the silo so that all parts will ferment alike. 
Comparatively short fermentation at a high temperature 
is preferable to slow fermentation at a low temperature. 



COMPOSITION OF COARSE FODDERS 



2 57 



Average Composition of American Fodders. 
(Jenkins and Winton.) 



Field-cured Fodders. ^ 

Pet. 

Corn fodder, average 42.2 

" minimum 22.9 

" maximum 60.2 

Corn leaves, average 30.0 

" minimum 14.8 

" maximum 44.0 

Corn stalks, average 68.4 

" minimum 51.3 

" " maximum 78.5 

Corn stover, average 40. 1 

11 " minimum 15.4 

" maximum 57.4 

Redtop 8.9 

Timothy : 

All analyses 13.2 

Cut in full bloom 15.0 

Cut soon after bloom 14.2 

Cut when nearly ripe 14. 1 

Red clover 15.3 

Alsike clover 9.7 

White clover 9.7 

Alfalfa 8.4 

Cowpea 10.7 

Wheat straw 9.6 

Oat straw 9.2 



1 

Pet. 

2.7 



c o 

I* 

Pet. 
4-5 

2.7 

6.8 
6.0 
4-5 
8-3 
1.9 

1.2 

3-° 

3-8 
1.8 

8.3 
7-9 

5-9 
6.0 

5-7 
5-o 
12.3 
12.8 
15-7 
14-3 
16.6 

3-4 
4.0 



3 u 

Pet. 
14-3 

7-5 
24.7 
21.4 
17.4 
27.4 
11. o 

6.9 
16.8 
19.7 
14.1 
32.2 
28.6 

29.0 
29.6 
28.1 

3i-i 
24.8 
25.6 
24.1 
25.0 
20.1 
38.1 
37.o 



a £■• 

bo X 

o <u 
U u 

MM (U 

Pet. 

34-7 
20.6 
47-8 
35-7 
27-3 
44.1 
17.0 
11. 2 
26.0 
3 1 -9 
23-3 
53-3 
47-4 

45-° 
41.9 
44.6 
43-7 
38.1 
40.7 

39-3 
42.7 
42.2 

43-4 
42.4 



-a *• 

w 2 

Pet. 
1.6 

0.6 

2-5 
1.4 
0.8 
2.2 
°-5 
o-3 
1.0 
1.1 
0.7 
2.2 
1.9 

2-5 

3-o 
3-o 

2.2 

3-3 
2.9 
2.9 
2.2 
2.9 
1-3 
2-3 



Green Fodders. 








Corn fodder (Flint) average . . . . 


. 79-8 


1.1 


2.0 


" " " minimum. . 


• 5i-5 


0.7 


0.6 


" " " maximum. . 


. 90.8 


1.8 


4.0 



4.3 12. 1 O.7 

2.1 4-3 0.3 
11. 4 36.3 1.3 



258 AGRICULTURAL CHEMISTRY 



S_- 



Green Fodders (continued). ^ < 

Pet. Pet. 

Corn fodder (Dent) average 79.0 1.2 

" " " minimum . . . 59.5 0.6 

" " " maximum. . . 93.6 2.5 

" " (Sweet varieties) ... 79.1 1.3 

" " (All varieties) 79.3 1.2 

Redtop in bloom 64.8 2.3 

Timothy 61.6 2.1 

Kentucky blue grass 65.1 2.8 

Legumes : 

Red clover 70.8 2.1 

Alfalfa 71-8 2.7 

Cowpea 83.6 1.7 

Soja bean 74.8 2.4 

Silage : 

Corn 79.1 1.4 1.7 6.0 11. 1 0.8 



'Bx 




<0 2- 
O « 

55 J3 




Pet. 


Pet. 


Pet. 


Pet. 


1.7 


5-6 


12.0 


0.5 


0.5 


2.0 


3-o 


O.I 


3-8 


11. 


27.0 


1.6 


1.9 




12.8 


0.5 


1.8 


5-o 


12.2 


o-5 


3-3 


9.4 


19.1 


1.2 


3-i 


11. 8 


20.2 


1.2 


4.1 


9.1 


17.6 


i-3 


4.4 


8.1 


13-5 


1.1 


4.8 


7-4 


12.3 


1.0 


2.4 


4.8 


7-i 


0.4 


3-o 


7-3 


n-5 


1.0 



CHAPTER XXIX 



Wheat 

379. Structure of Kernel. — The wheat kernel has three 
distinct coverings (see Fig. 88) : (1) The outer cuticle or 
.pericarp, which is a hard, tough coat, composed largely of 
ligno-cellulose ; this is the seed pod inclosing the seed, 
and constitutes the main part of the bran. (2) An inner 
double cuticle of cellular tissue called the episperm, con- 
sisting of two hard coats called respectively the inner and 




Fig. 88. — Structure of wheat kernel : 1 , floury portion ; 2, aleurone layer ; 3, the 
bran composed of three layers ; 4, germ (adapted from Bull. 32, Neb. Exp. 
Station) . 

outer integument ; this double skin or layer may be 
considered one coat and forms part of the bran. (3) A 
hard, thin skin or layer called the perisperm. The three 
bran coats constitute about 5 per cent of the weight of 
the grain. Within these three bran layers is a single 
layer of large cells, the aleurone layer. This is sometimes 
erroneously termed the gluten layer. The germ or 

259 



260 AGRICULTURAL CHEMISTRY 

embryo plant is in the lower part of the kernel opposite 
the rounded end. The main part of the seed is the 
endosperm, which is the floury portion, sometimes incor- 
rectly spoken of as the starch cells, in reality composed of 
starch, gluten, mineral matter, and other compounds in 
small amounts. 

380. Proteids of Wheat. — Wheat contains the largest 
amount of proteids of any of the cereals, and proteids 
of an entirely different character from those of other 
grains. There are five distinct proteids in wheat : (1) an 
albumin (leucosin), (2) a globulin (edestin), (3) a prote- 
ose, and two insoluble proteids called (4) gliadin, and 
(5) glutenin, which together constitute the gluten. Wheat 
gluten may be obtained by washing a sample of dough 
from wheat meal or flour with water to remove the starch 
and other non-gluten compounds. The gluten mass from 
hard wheat is usually elastic and tenacious, varying in 
quality according to the nature of the wheat from which 
it was obtained. The milling qualities of wheat and the 
baking qualities of flour are determined largely by the 
composition of the gluten. 

Wheat gluten is composed of two proteids, gliadin and 
glutenin; these form about 85 per cent of the proteids 
of wheat. Gliadin may be extracted from either gluten 
or flour with a 70 per cent solution of alcohol, and appears 
after evaporation of the alcohol in the form of thin, trans- 
parent flakes which resemble gelatin. In fact, gliadin 
was called by earlier investigators plant gelatin. When 
moistened, gliadin expands and forms a mucilagenous 
mass. When more water is added, a small amount is 
dissolved. Gliadin is soluble in dilute acid and alkali 
solutions ; in some wheats, particularly those that have 
undergone slight fermentation, there is sufficient acid 



WHEAT 26l 

developed to combine with and render soluble appreciable 
amounts. Gliadin, like all the wheat proteids, is charac- 
terized by a high per cent of nitrogen. Gliadin takes 
a very important part in bread making, and is the material 
which binds the. flour together to form dough and enables 
the mass to expand, retaining the gas generated by the 
yeast. Wheat gluten contains from 40 to 75 per cent of 
gliadin and from 25 to 60 per cent of glutenin. 

Glutenin is the proteid which remains after extracting 
gliadin from gluten. When dry and pure, it forms a 
light gray mass which may be reduced to a fine powder. 
Glutenin is insoluble in dilute alcohol and salt solutions 
and is only sparingly soluble in water, but is readily soluble 
in dilute acid and alkali solutions. This proteid also 
takes an important part in bread making. It combines 
mechanically with the gliadin and, " serving as a nucleus 
to which the gliadin adheres," prevents the dough from 
becoming too soft and sticky. Two samples of wheat 
may contain the same amount of gluten, and the flour 
from one produce good bread, while that from the other 
be of very poor quality. The most valuable wheats for 
bread-making purposes are those which have 12 per 
cent or more of protein. A wheat may produce a good 
quality of bread and contain only a medium per cent of 
protein, while, on the other hand, poor bread-making 
qualities may be associated with a high per cent of protein. 
Glutens considered the most valuable for bread-making 
purposes are hard, elastic, and of a light yellowish tinge. 
Poor gluten is dark in color, has an uneven surface, 
possesses but little power to recoil, and may be very 
sticky. 

Gliadin and glutenin contain about 1 7 per cent nitrogen, 
one part of nitrogen to 5.70 of protein (100 4- 17.50). 



262 AGRICULTURAL CHEMISTRY 

Average proteids have approximately 16 per cent nitrogen 
and a protein conversion factor of 6.25 (see Section 307). 
In scientific work the protein of wheat is sometimes calcu- 
lated as N X 5.70, which means that the special factor 
5.70 instead of the general factor 6.25 is used. For 
general nutritive purposes, however, the 6.25 factor should 
be employed, inasmuch as special factors are not used 
for other foods. In the case of wheat with a proteid 
more concentrated in nitrogen, if 5.70 and not 6.25 were 
used, too low a food value would be assigned compared 
with other foods having a proteid less concentrated in 
nitrogen, for it is the nitrogenous part of the molecule 
which gives the unique food value to the proteids, and 
if the special conversion factor is used for calculating 
protein in wheat or other food, then the individual value 
of wheat protein must be considered in making com- 
parisons and assigning food values. It is believed that 
the general factor 6.25 represents for comparative nutritive 
purposes the value of the proteids, as it expresses the 
protein content on a uniform basis of concentration of 
the molecule in nitrogen, and dispenses with giving sep- 
arate value to each protein. 

Experiment 69. — Gluten from wheat flour. To about 30 grams 
of flour made from hard spring wheat, add sufficient water to form 
a stiff dough and allow it to stand for half an hour, in order that 
the physical properties of the gluten may develop. Place the dough 
in a cloth and work it gently with the fingers, while a stream of 
water is allowed to flow over it. Continue the washing until the 
water that runs away is clear, which indicates that all starch has 
been washed from the dough. The washing may be completed 
with the mass in the hand. Leave this gluten in water until the 
gluten from flour made from soft winter wheat has been prepared. 
Compare the two samples of gluten. 

Questions. — (1) What is wheat gluten ? (2) Describe hard wheat 
gluten. (3) How does it differ from soft wheat gluten ? (4) How 



WHEAT 263 

do the two moist glutens compare as to weight ? (5) Which gluten 
contains the larger amount of gliadin ? (6) Which is the better 
quality of gluten for bread-making purposes ? 

Experiment 70. — Gliadin from flour. Place in a flask 10 grams 
of flour, 30 cc. of alcohol, and 20 cc. of water. Cork the flask and 
shake, and after a few minutes shake again. Allow the alcohol to 
act on the flour for an hour, or until the next day. Then filter off 
the alcohol solution and evaporate the filtrate to dryness over the 
water bath. Examine the residue. To a portion add a little water. 
Burn a little. Treat a little in a test tube with water containing a 
few drops of HC1. 

Questions. — (1) Describe the appearance of the gliadin. (2) What 
was the result when water was added ? (3) When burned, what 
was the odor of the gliadin, and what does this indicate ? (4) What 
effect did the dilute HC1 have upon the gliadin ? (5) What is 
gliadin ? 

381. Relation of Nitrogen in Wheat to Nitrogen Con- 
tent of Flour. — Medium-sized, amber-colored, hard, 
well-formed wheat kernels usually contain more nitrogen 
and gluten than large, rotund kernels. The size of the 
germ, the proportion of aleurone to endosperm, and the 
nitrogen content of the endosperm or floury portion are 
the three factors which determine the relation of the 
nitrogen in wheat to the nitrogen in flour. Ordinarily, 
the bran and offal make up about 25 per cent of the weight 
of the kernel, and the endosperm from 75 to 80 per cent. 
When the amount of endosperm is increased, there is 
proportionally less offal and more flour. The size of the 
wheat kernel, together with the size of the indentation 
marking the germ area, indicate approximately the amount 
of germ in the kernel. The larger the per cent of germ 
and aleurone, the smaller the amount of flour recovered 
when the wheat is milled. As a general rule, wheats which 
contain the most nitrogen produce the most nitrogenous 
flours, but the total nitrogen in the wheat cannot always 



264 



AGRICULTURAL CHEMISTRY 



be taken as an index of that in the flour. Two wheats may 
contain about the same total nitrogen and the nitrogen be 
distributed differently in each, — in one a larger portion 
being present in the offal, and in the other more in the 
endosperm and hence recovered as flour. In the follow- 
ing table are given the percentages of protein in the 
grain and in the patent flour by the modern roller process 
of milling. These tests were made under the supervision 
of the author in large flour mills of Minneapolis, Minn. 
The percentage amount of the wheat recovered as patent 
flour was about the same in all of the tests. 





Per Cent of Protein. 




Mill B. 




Wheat. 




Flour. 


15-19 




14.60 


15-44 




14-13 


15-75 


Mill C. 


14.00 


I5-50 




13.90 


15.38 




14.65 


14-33 




13.88 


15.51 




14.44 


15.00 




13-94 


I5-I5 




14.06 


I5-I9 




14.19 



382. Influence of Fertilizers upon Composition of 
Wheat. — Experiments by Lawes and Gilbert (Rotham- 
sted Memoirs, Vol. Ill) show that the different kinds of 
manure, as nitrogenous, mixed, and mineral, influence 
the yield but not materially the composition of the grain. 
During the time of the experiment, covering a period of 
twenty years, the nitrogen, phosphoric acid, and potash 
in the dry matter of the grain were fairly constant, and 
when different manures were used, there were no greater 



WHEAT 265 

variations in the composition of the grain than between 
crops upon the same plots similarly manured during 
different seasons. Climatic conditions influenced the 
composition of the kernel to a greater extent than did 
fertilizers. Fertilizers, however, exert an influence upon 
commercial grade and bread-making value of wheat to a 
greater extent than is reflected by chemical analysis of 
the wheat. 

383. Variations in Composition of Wheat. — In Jenkins 
and Winton's " Average Composition of American Feed- 
ing Stuffs," spring wheat is given as containing 12.5 per 
cent protein and winter wheat 11.8 per cent. In both 
spring and winter wheat there are variations in protein 
content from 8 to 16 per cent. While average wheat 
is given as containing 12.5 per cent, later analyses show 
some to contain as high as 19 per cent. 

The greatest differences in composition are noticeable 
between wheats grown in different seasons. Five samples 
of the 1 89 1 crop of wheat analyzed by the author at the 
Minnesota Experiment Station contained 12.01 per 
cent of protein. The wheat was of high milling and bak- 
ing value. In 1892, six samples from the same localities 
showed 13.22 per cent of protein, and in 1901, 14 samples 
contained 15.21 per cent. 

Some of the effects of climate and soil upon the physical 
and chemical properties of wheat are noted in Bulletin 
No. 18, Part 9, Division of Chemistry, United States 
Department of Agriculture, from which the following 
paragraphs are taken : 

" The inherent tendency to change which is found in 
all grains is most prominent in wheat ; it may be fostered 
by selection and by modifying such of the conditions of 
environment as it is in the power of man to effect. The 



266 AGRICULTURAL CHEMISTRY 

most powerful element to contend with is the character 
of the season or unfavorable climatic conditions. The 
injury done in this way is well illustrated in Colorado, 
and it would seem advisable in such cases to seek seed 
from a source where everything has been favorable, and 
begin selection again. It must be borne in mind that 
selection must be kept up continuously, and that reversion 
takes place more easily than improvement. Hallett, 
in England, was able to make his celebrated pedigree 
wheat by selection, carried on through many years, but 
the same wheat grown by the ordinary farmer under 
unfavorable conditions for a few years without care has 
reverted to an ordinary sort of grain. 

" The effect of climate is well illustrated by four speci- 
mens of wheat which are to be seen in the collection of 
the Chemical Division. Two of these were from Oregon 
and Dakota some years ago, and present the most ex- 
treme contrast which can be found in this variable grain. 
One is light yellow, plump and starchy, and shows on 
analysis a very small per cent of albuminoids ; the other 
is one of the small, hard, and dark-colored spring wheats 
of Dakota, which are rich in albuminoids. Between these 
stand two specimens from Colorado, which have been 
raised from seed similar to the Oregon and Dakota wheat. 
They are scarcely distinguishable except by a slight 
difference in color. The Colorado climate is such as to 
have modified these two seed wheats, until after a few 
years' growth they are hardly distinguishable in the 
kernel. All localities having widely different climates, 
soils, or other conditions produce their peculiar varieties 
and modify those brought to them. The result of these 
tendencies to change and reversion from lack of care in 
seed selection or other cause has led to the practice of 



WHEAT 267 

change of seed among farmers. A source is sought where 
either through greater care or more favorable conditions 
the desired variety has been able to hold its own. Some- 
times this change is rendered necessary by conditions 
which are beyond the power of man to modify. As an 
example, No. 10 of Professor Blount's wheats, known as 
1 Oregon Club,' a white variety from Oregon, has been 
deteriorating every year since it has been grown in Colo- 
rado, whereas if the seed had been supplied every season 
directly from Oregon, the quality would probably have 
remained the same. In extension of this illustration the 
fact may be mentioned that the annual renewal of the 
seed from a desirable and favorable source often makes it 
possible to raise cereals where otherwise climatic con- 
ditions would render their cultivation impossible through 
rapid reversion. This is particularly the case with 
extremes in latitude, the effect of which is not founded 
so much upon the composition of the crop as on the yield 
and size of the grain." 

The water supply of a crop during growth greatly 
influences its composition. Irrigated wheats, grown with 
excess of water, have large, starchy kernels. With a 
limited amount of water the kernels are smaller, darker- 
colored, and harder. Wheats raised by " dry farming " 
methods of cultivation are richer in protein than the 
same class of wheats grown by irrigation. 

384. Storage of Wheat in Elevators. — New wheat 
is subjected to a fermentation change known as " sweat- 
ing." This affects, to a slight extent, the chemical com- 
position and improves the milling qualities of the grain. 
When wheat is damp, the fermentation may cause the 
temperature to rise high enough to cause spontaneous 
combustion. Thoroughly sound wheat undergoes but 



268 AGRICULTURAL CHEMISTRY 

little change in temperature even when stored in large 
elevators where 120,000 bushels are placed in one tank. 
The changes during storage are brought about by the 
enzymes or soluble ferments in the grain and the organized 
ferments and molds that are present on the surface of 
the grain. When wheat has been thoroughly cleaned, it 
does not readily undergo fermentation, while uncleaned, 
damp, and unsound wheats deteriorate. 

385. Manufacture of Wheat into Flour. — The manu- 
facture of wheat flour is a mechanical process. The 
cleaned wheat is broken into pieces at the first break- 
rolls, and is separated by means of sieves (bolters) into a 
number of grades of stock of varying size, as bran flakes, 
pieces of flattened and cracked wheat, coarse and fine 
middlings, masses of flour particles about the size of 
granulated sugar, and a little flour and flour dust. The 
residue of cracked wheat is reduced to finer particles at 
the second break, and separated into products similar 
to the first break bolting. The process of reducing the 
residue is repeated until the flour is removed from the 
bran. The various middlings stocks pass in thin layers 
over long stretches of silk bolting cloth, where carefully 
regulated air currents lift out the fine fibrous material 
and dust while the heavier flour granules are bolted or 
passed through the cloth. These purified middlings are 
then reduced to flour by means of smooth rolls and form 
the basis of the patent grades of flour. When all the mer- 
chantable flour is recovered as one product, it is called 
straight grade or standard patent flour. If it is sepa- 
rated into two or more parts, it is designated as patent 
and clear, or first and second patent and first and second 
clear. (See Section 411 for wheat by-products.) 

386. Composition of Unsound Wheat. — When wheat 



WHEAT 269 

fails to fully mature or is affected by frost, fungus disease, 
as rust or smut, or excessive heat, causing bleaching, the 
composition of the kernel is affected. Such wheats may 
contain a larger percentage of soluble carbohydrates, 
organic acids, and soluble proteids than fully matured 
wheat. Wheats damaged by bleaching, frost, or fungus 
disease give lower yield of flour with poorer keeping and 
bread-making qualities. Frost and excessive heat affect 
the physical qualities of the gluten. 

387. Composition of Different Varieties of Wheat. — 
The different varieties of wheat, as spelt and durum, are 
similar in general composition to ordinary wheat with 
variations in quality of gluten. In durum, as in other 
wheats, the percentage of protein varies with the con- 
ditions under which the grain is grown. In the table 
given at the close of this chapter, it will be seen that 
durum has about the same content of proteid matter and 
other nutrients as hard spring wheat grown under similar 
conditions. Winter wheats generally contain less protein 
than spring wheats. Large, light-colored kernels contain 
less protein than darker-colored amber, denser, and 
more corneous kernels of the same variety. 

Experiment 71. — Grading wheat. Make the following test with 
three samples of wheat. (1) Obtain the weight per quart (dry 
measure), and then calculate the weight per bushel of each. 
(2) Weigh 100 kernels of each sample. (3) Place ten representative 
kernels (of each) end to end and measure the length in millimeters 
and inches. (4) Note the color and appearance of each sample. 
(5) Observe if the kernels are "well filled"; (6) free from weed 
seeds, and if there are any indications of smut, frosting, or bleach- 
ing. (7) Assign a grade to each sample (see Section 409). 

388. American and Foreign Wheats. — A compilation 
of analyses of wheats and of other cereals grown in dif- 
ferent countries has been made by Konig. Absolute 



270 AGRICULTURAL CHEMISTRY 

comparisons as to composition cannot be made because of 
numerous local factors which affect the wheat, as climate 
and soil. As great a difference is found in the composi- 
tion of wheats raised in various parts of the United States 
as between those of different countries where there exist 
similar varieties of climate and soil. In the case of 
American wheats, the tables given were compiled before 
any large number of northwestern wheats were analyzed, 
hence the protein content is low because so small a number 
of wheats of highest protein content are included in the 
averages. In general, the tables of analyses show that 
wheat grown in tropical climates is less nitrogenous than 
that grown in more northern latitudes on equally fertile 
soils. In making use of the figures given in the follow- 
ing tables, it should be remembered that the comparisons 
are only relative, as some of the samples contain a much 
larger amount of moisture than others ; and samples 
proportional to the wheat-growing regions are not in- 
cluded in the averages. 

389. Wheat as Animal Food. — Wheat is not generally 
used for fattening farm animals, because of its high market 
value. Occasionally, however, it is more economical to 
use it in preference to other grains for the feeding of 
stock. Experiments show that it has a high feeding value. 
As a food for growing pigs, it is somewhat preferable to 
corn ; for fattening pigs, there is but little difference 
between wheat and corn. The best results are obtained 
when wheat is ground and fed with other grains. A 
mixture of equal parts of ground wheat and corn gives 
better results than either wheat or corn fed alone. When 
the price of wheat is low and it can be purchased for the 
same or less per pound than corn, it will pay to use it 
for feeding farm animals. As a food for dairy animals^ 



WHEAT 271 

ground wheat is fully equal to either corn or a mixture of 
corn and barley. When fed to fattening steers, ground 
wheat produces about the same results as ground corn. 

390. Wheat as Human Food. — Wheat is used as human 
food more extensively than any other cereal. This is 
due largely to its production over wider ranges of latitude 
and its containing proteids specially adapted to bread 
making. With the exception of rye, wheat is the only 
grain that contains gliadin, the proteid which forms 
the dough and with the gas causes expansion of the mass 
during the bread-making process. 

" Among all civilized nations bread, in its broad sense, 
is the basis of human nutrition, all dietary standards 
cluster about it as the center and support of the system 
of nutrition. Not only is it the most important, but at 
the same time it is the cheapest of nutrients. Measured 
by actual nutritive power there is no other complete 
ration which in economy can compare with bread." 1 

Composition of Wheat 

(Jenkins and Winton, and Konig's works) 

& U a w S £■£ uS < 

Pet. Pet. Pet. Pet. Pet. Pet. 

Wheat, spring 10.4 12.5 2.2 71.2 1.8 1.9 

Wheat, spring (max.) 13.4 15.4 2.6 78.7 2.3 2.6 

Wheat, spring (min.) 8.1 8.1 1.8 66.1 1.3 1.5 

Wheat, winter 10.5 11. 8 2.1 72.0 1.8 1.8 

+ Wheat, spelt 2 10.0 11.3 2.3 63.9 9.2 t>'3 

-f- Wheat, durum 3 10.7 15.0 2.4 (69.9) 2.0 

+ Wheat, hard fife 4 11. 2 15.8 2.3 (68.8) 1.9 

1 H. W. Wiley, Bui. 13, Part IX, U. S. Dept. Agr. Div. Chem. 

2 Minn, analyses. 3 Average of thirteen northern grown samples. 
4 Spring wheat grown under similar conditions as durum. 



272 



AGRICULTURAL CHEMISTRY 



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CHAPTER XXX 



Maize (Indian Corn) 

391. Structure of the Kernel. — Corn has somewhat 
the same general structure as wheat. The seed coat, how- 
ever, is composed of two instead of three layers (see Fig. 
89). Within the seed coat or hull (1) there is a hard 
aleurone layer (2) which is 
thicker at the sides than at 
the crown. The floury 
portion (4), which. is usu- 
ally hard and flinty, is the 
larger part of the kernel, 
while the germ (3) con- 
stitutes about 10 per cent 
of the weight. The pro- 
portional amounts of germ, 
floury portion, and aleu- 
rone layer differ with in- 
dividual samples. The 
hulls make up about 5.5 
to 6 per cent of the kernel, 
while about 85 per cent 
is floury portion and aleu- 
rone layer. In the milling 
of corn, as in the milling of 
wheat, a mechanical separation of the different parts 
is effected. 

392. Composition of Corn. — Corn is fairly constant in 

T 273 




Fig. 89. — Structure of corn kernel : 
1, seed coat; 2, aleurone layer; 3, 
germ ; 4, floury portion (adapted from 
N. J. Expt. Station Bull.). 



2 74 AGRICULTURAL CHEMISTRY 

composition. As the result of a large number of analyses 
made by the Department of Agriculture, the following 
conclusion is drawn : " A study of all the analyses which 
have been made reveals the fact that maize is one of the 
most un variable of the cereals, maintaining under the 
most different climatic conditions a most remarkable uni- 
formity of composition, varying chiefly in the size, color, 
and general physical characteristics of its kernels rather 
than in their composition." 

From the figures given at the close of the next chapter 
it will be observed that corn contains a much larger 
amount of fat than wheat, also somewhat less protein ; 
the nitrogen-free extract, which is mainly starch, is about 
the same in amount in both. Investigations at the 
Illinois Experiment Station show that all the kernels 
upon the same ear are fairly constant in composition, 
although the kernels on the tip of the ear have a tendency 
to contain slightly less protein than those either in the 
middle or at the base ; the difference in both protein 
and carbohydrates in a few extreme cases was about i per 
cent. The composition of the kernel is slightly influenced 
also by the stage of maturity. If, for any reason, corn 
fails to reach full maturity, there is usually more protein 
and less carbohydrates in the dry matter. 

393. Proteids of Corn. — The proteids of corn are quite 
different in character from those of wheat. Small amounts 
of albumin and globulin are present, but the larger portion 
of the corn proteids is in insoluble forms called zeins, 
one of which is soluble and the other insoluble in alcohol. 
The zeins differ both in physical and chemical composition 
from wheat gliadin. The corn proteids contain about 1 
part nitrogen to every 6.23 parts proteid material, while in 
wheat there is about 1 part nitrogen to 5.7 proteids. 



MAIZE 



275 



394. Glutenins and Starchy Corn. — The germ and 
aleurone layers are more nitrogenous in character than 
the interior or floury portion of the kernel. Since the 
proportion or germ and aleurone in corn, as in wheat, varies 
with individual samples, the nitrogenous matter, being 
greater in these parts, also varies. Taking advantage of this 
knowledge, it is possible, 
by mechanical means, to 
distinguish corn samples 
of high from those of 
low proteid content. 
The Illinois Experiment 
Station directs attention 
to this fact in Bulletin 55. 

" By making cross 
sections and longitudinal 
sections of several kernels 
from an ear of corn, one 
can judge, with a very 
satisfactory degree of 
accuracy, whether the 
corn is rich or poor in 

protein. The illustration Fig. 90. — Nitrogenous and non-nitrogenous 

(Fig. 00) here shown was corn : r > < r orn with I4 - 92 per cent proteln ; 

• ° r 2, corn with 7.76 per cent protein. 

made from a photograph 

taken of the corn kernels and sections with a magnification 
of three diameters. At the left are two sections and a whole 
kernel from corn containing 14.92 per cent of protein. The 
sections and kernel at the right are from corn containing 
7.76 per cent of protein. About one fourth of the kernel 
was cut off from the tip end in making the cross sections. 
In the longitudinal sections the tip end of the kernel 
points upward to the right. It will be seen that in the 




276 AGRICULTURAL CHEMISTRY 

cross sections the white starchy layer nearly disappears 
in the high-protein corn, but becomes very prominent in 
the low-protein corn. In the longitudinal sections this 
difference is also apparent, the white starch in the high- 
protein corn being confined almost entirely to the crown 
end of the kernel, while in the low-protein corn it extends 
into the tip end in considerable amount. The germ 
in the high-protein corn is somewhat larger. This is 
also indicated by the depressions in the whole kernels." 
There are occasionally exceptions, however, in the 
relation of form to the protein content of corn, but 
in making comparisons in the manner indicated, the few 
errors liable to occur are in assigning too low rather than 
too high a protein value to the sample. In the selection 
of seed corn a knowledge of the characteristic of the 
kernels as of high- or low-protein content will be found of 
value. 

Experiment 72. — Select, from a sample of corn, kernels of highl- 
and kernels of low-protein content. Make longitudinal and cross 
sections of some of the kernels, and note the proportion of germ, 
aleurone, and floury parts in each. Make a drawing of a represen- 
tative kernel of each kind of corn. Observe how your rating of the 
corn compares with the chemical analysis. Determine the weight 
per bushel and assign a grade to the sample. 

395. Varieties of Corn. — The numerous analyses, 
which have been made of the different varieties of corn as 
dent or flint, do not show any wide variations in com- 
position when they are grown under similar conditions. 
The main differences are in the amount of coloring matter 
and in the physical characteristics rather than in chemical 
composition. Yellow corn contains no more nutrients 
than white corn ; there is coloring matter present in one 
and not in the other. Sweet corn contains more sucrose, 



MAIZE 



277 



but otherwise it has about the same general composition 
as the dent and flint varieties. 

396. Moisture Content of Corn. — The keeping qualities 
of corn depend largely upon 
its moisture content. With 
more than 19 per cent mois- 
ture, corn cannot be con- 
sidered safe for storage. 
With a sufficiently high tem- 
perature corn " heats " or 
ferments with less than 19 
per cent moisture. The 
moisture in corn is deter- 
mined for commercial pur- 
poses, in the following way : 

One hundred grams of corn 
are placed in flask (a), with 
100 cc. of thin lubricating 
oil that has a high ignition 
point (a commercial grade 
known as " Atlantic red " 
being suitable for the pur- 
pose). The stopper with 
thermometer (b) and delivery 
tube (c) is inserted. The 
delivery tube is connected 
with condenser (d) and the 
graduated cylinder (e) is 
placed so as to receive the dis- 
tillate. Heat is applied gradually until the thermometer 
registers 188 C. and then is shut off. The cc. of distillate 
in the graduate represents the per cent of moisture in the 
corn . This method , first used by a German chemist , has been 




Fig. 90a. — Grain moisture. 

Apparatus. A block tin pipe (d) 
passes through a condensing cham- 
ber filled with water. The flask (a) 
rests upon a triangle supported by 
a metal frame or box of galvanized 
iron with a perforated lid at (g) . The 
box is lined with asbestos paper. 



278 AGRICULTURAL CHEMISTRY 

modified, and is generally referred to as the " government " 
moisture method. It is extensively used in the testing of 
corn, and is also applicable to the testing of wheat for 
moisture content. 

397. Corn Products. — When the entire kernel is 
ground, coarse corn meal is the product. When a part 
of the bran is removed, fine corn meal is obtained. Corn 
flour is made by removing the bran and germ and reduc- 
ing the interior portion of the kernel, as in flour making. 
In the manufacture of starch, the proteid matter is 
removed, and with the germ and bran, forms the basis 
of a number of commercial feeds. Cornstarch is sold 
either as a commercial product, or is used in the prepa- 
ration of glucose (see Experiment 49). The larger por- 
tion of the fat or oil of corn is present in the germ and 
is recovered as corn oil. A number of other products 
are also obtained from corn. 

398. Corn as a Food. — Corn is extensively used both 
as human and animal food. Its proteids do not render 
it as valuable for bread-making purposes as wheat. It 
is, however, one of the cheapest foods that can be procured, 
and the prejudice against its use as human food because 
of its being fed to animals is gradually being overcome. 
Its value as animal food is too well known to require 
further discussion. 



CHAPTER XXXI 

Oats, Barley, Rye, Buckwheat, Rice, and 
Miscellaneous Seeds 

399. Structure of the Oat Kernel. — Oats are composed 
of two parts, the kernel and the hull. The hulls have 
the same general composition as straw, and make up 
about 30 per cent of the weight. The different parts of 
the oat kernel are: (1) seed pod, (2) aleurone layer, 
(3) germ, and (4) floury portion. The weight per bushel 
of oats depends largely upon the amount of hulls ; in some 
samples these make up 25 per cent, and in others 35 per 
cent of the weight. 

400. Composition of Oats. — When the hulls are 
included, oats have a larger amount of fiber and ash than 
any other cereal. The per cent of fat is higher than in 
wheat, barley, or rye, and as high as in corn. Hulled 
oats have about the same general composition as wheat, 
with a tendency to a higher protein content. They are 
also characterized by a high per cent of fat. Variations 
in the composition of oats are, to a limited extent, notice- 
able. The ratio of hull to kernel influences the composi- 
tion more than any other factor. There is not a great 
difference in the chemical composition of heavy- and 
light-weight oats. Experiments at the Maine Experi- 
ment Station show that the differences are mainly in the 
amount of nutrients in a given, volume of the grain, as 
a bushel, rather than in percentage composition. This 
emphasizes the importance of feeding oats by weight 
rather than by measure. 

279 



280 AGRICULTURAL CHEMISTRY 

401. Oats as Human and Animal Food. — Oats are used 
more extensively as an animal food than as human food. 
When the hulls are removed and the oats are properly 
prepared, they make a valuable human food, because of the 
large amount of available protein, fat, and other nutrients. 
Oats are especially well adapted for the feeding of horses, 
because of their mechanical condition and the character 
of the available nutrients. Experiments at the Wisconsin 
Exp. Station show that when fed to dairy animals under 
similar conditions, high grade oats produce 10 per cent more 
milk and butter fat than the same weight of average bran. 

402. Barley is used largely for brewing and for animal- 
feeding purposes rather than as a human food. There is 
less fat, fiber, and ash than in oats, but more protein and 
carbohydrates. Barley contains less protein than wheat. 
For brewing purposes, perfectly sound and fully matured 
barley with a high germination percentage is necessary, 
while that which has been slightly damaged in any way, 
as by rain, frost, or hot winds, is not suitable for this 
purpose. Such barley, however, can be used for feeding 
purposes, and is often the cheapest grain that can be fed 
by western farmers. Barley is suitable for feeding to 
all kinds of farm animals. The hull-less varieties contain 
less fiber and more protein and available carbohydrates. 
A study of the proteids of barley shows that there is 
about 1 part of nitrogen to every 5.7 parts of protein, 
which is practically the same in amount as is found in 
wheat proteids. 

403. Rye. — Rye contains proteids similar to wheat, 
rendering it suitable for bread-making purposes. How- 
ever, rye is more extensively used in this country for the 
manufacture of alcoholic beverages than for bread. Rye 
resembles wheat in chemical composition more than does 



OATS, BARLEY, RYE, ETC. 281 

any other cereal, although when grown under similar 
conditions it contains somewhat less protein than wheat. 
In the feeding of farm animals, rye must be used with 
more caution than wheat. If used in a dairy ration in too 
large amounts, it is believed to have a tendency to pro- 
duce a slightly inferior quality of milk and butter, but 
when fed moderately no difficulty is experienced. In 
a mixed ration, rye has been found equal to barley and 
other cereals for meat production. 

404. Rice. — Rice is characterized by a low protein and 
fat content, and a high per cent of carbohydrates. It is 
not used to any extent for the feeding of stock, although 
its by-products are employed for this purpose. Rice 
may furnish the carbohydrates of a ration at a low cost, 
but should be combined with foods rich in protein, as 
legumes. 

405. Buckwheat. — The entire kernel contains quite 
an appreciable amount of fiber, which is removed in the 
preparation of buckwheat flour. There is somewhat 
less protein than in wheat and other cereals. Buckwheat 
is not extensively used for the feeding of animals, although 
some of its by-products are valuable for this purpose. 

406. Flax is a type of oil seed, small in size but with a 
large amount of nutrients in the form of fat. Average 
flax contains about 38 per cent of fat, which is largely 
removed in the manufacture of linseed oil. A bushel of 
flax will yield about 19 pounds of oil and 40 pounds of 
oil cake. Flax is too concentrated, and usually too 
valuable a market crop to be used much for animal feeding 
purposes. Should the price warrant, it may be combined 
with other grains. As much as 8 pounds a day have 
been fed in a dairy ration without apparent ill results. 
Unripe and immature flaxseed is often used for feeding 



282 AGRICULTURAL CHEMISTRY 

purposes. Other oil seeds, as cotton and rape, are valu- 
able for the oil they contain, and the oil cake which is 
used for feeding purposes. 

407. Millet Seed has somewhat the same general com- 
position as oats. However, when fed it should be ground 
and combined with other grains. 

408. Peas and Beans. — Peas and beans, as well as 
other leguminous seeds, are characteristically rich in 
protein and contain variable amounts of fat. Peas and 
beans are valuable alike as human and animal food. 
When used as animal food, they should form a part 
of a grain ration. They are particularly good for pork 
production as well as for meat and milk, but their high 
price usually prevents their extensive use in animal 
feeding. When they can be produced cheaply and 
abundantly, they are among the best foods that can be 
used. The proteid of leguminous seeds is largely in the 
form of legumin, a casein-like body. 

409. Grading of Grains. — Oats, barley, rye, and other 
grains are all graded commercially on the basis of their 
physical properties, as weight per bushel, maturity, 
amount of foreign weed seed, and any fungus disease, or 
injury caused by rust or excessive heat. As an example 
of rules for grading grain the following adopted by the 
Minnesota Board of Grain Appeals are given. 

NORTHERN SPRING WHEAT 

No. 1 Hard Spring Wheat. — Shall be dry, sound, bright, sweet, 
clean, and consist of over 50 per cent of the hard varieties, and 
weigh not less than 58 pounds to the measured bushel. 

No. 1 Northern Spring Wheat. — Shall be dry, sound, sweet, 
and clean, may consist of the hard and soft varieties of spring wheat, 
and weigh not less than 57 pounds to the measured bushel. 

No. 2 Northern Spring Wheat. — Shall be dry, spring wheat, 



OATS, BARLEY, RYE, ETC. 283 

not clean enough or sound enough for No. 1, but of good milling 
quality and must not weigh less than 56 pounds to the measured 
bushel. 

No. 3 Northern Spring Wheat. — Shall be composed of inferior, 
shrunken spring wheat and weigh not less than 54 pounds to the 
measured bushel. 

No. 4 Northern Spring Wheat. — Shall include all inferior 
spring wheat that is badly shrunken or damaged and weigh not less 
than 48 pounds to the measured bushel. 

Rejected Spring Wheat. — Shall include all varieties of spring 
wheat sprouted, badly bleached or for any other cause unfit for 
No. 4. 

Note. — Hard, flinty wheat, of good color, containing no appre- 
ciable admixture of soft wheat, may be admitted into the grades 
of No. 2 Northern Spring Wheat and No. 3 Northern Spring Wheat, 
provided weight of the same is not more than one pound less than 
the minimum test weight required by the existing rules of said 
grades, and provided, further, that such wheat is in all other respects 
qualified for admission into such grades. 

Note. — The variety of wheat known as "Humpback," owing to 
its inferior milling quality, shall not be graded higher than No. 3. 

WHITE WINTER WHEAT 

No. 1 White Winter Wheat. — Shall include all varieties of 
pure, soft, white winter wheat, sound, plump, dry, sweet, and clean, 
and weigh not less than 58 pounds to the measured bushel. 

No. 2 White Winter Wheat. — Shall include all varieties of soft, 
white winter wheat, dry, sound, and clean, may contain not more 
than 5 per cent of soft red winter wheat, and weigh not less than 56 
pounds to the measured bushel. 

No. 3 White Winter Wheat. — Shall include all varieties of 
soft, white winter wheat, may contain 5 per cent of damaged grains 
other than mow-burnt wheat, and may contain 10 per cent of soft 
red winter wheat, and weigh not less than 53 pounds to the meas- 
ured bushel. 

HARD WINTER WHEAT 

No. 1 Hard Winter Wheat. — Shall include all varieties of hard 
winter wheat, sound, plump, dry, sweet, and clean, and weigh not 
less than 61 pounds to the measured bushel. 



284 AGRICULTURAL CHEMISTRY 

No. 2 Hard Winter Wheat. — Shall include all varieties of hard 
winter wheat, dry, sound, and clean, and weigh not less than 59 
pounds to the measured bushel. 

No. 3 Hard Winter Wheat. — Shall include all varieties of hard 
winter wheat, of both light and dark colors, not clean and plump 
enough for No. 2, and weigh not less than 55 pounds to the measured 
bushel. 

No. 4 Hard Winter Wheat. — Shall include all varieties of hard 
winter wheat not fit for a higher grade. 

RED WINTER WHEAT 

No. 1 Red Winter Wheat. — Shall be pure red winter wheat of 
both light and dark colors, dry, sound, sweet, plump, and well 
cleaned, and weigh not less than 60 pounds to the measured 
bushel. 

No. 2 Red Winter Wheat. — Shall be red winter wheat of both 
light and dark colors, shall not contain more than 5 per cent of 
white winter ; dry, sound, sweet, and clean, and weigh not less than 
58 pounds to the measured bushel. 

No. 3 Red Winter Wheat. — Shall be sound red winter wheat, 
not clean and plump enough for No. 2 ; shall not contain more than 
5 per cent of white winter, and weigh not less than 5 5 pounds to the 
measured bushel. 

WESTERN WHITE AND RED WHEAT 

No. 1 Western White Wheat. — Shall be dry, sound, well 
cleaned, plump, and composed of the western varieties of white 
wheat. 

No. 2 Western White Wheat. — Shall be dry, sound, reason- 
ably clean, and composed of western varieties of white wheat. 

No. 3 Western White Wheat. — Shall be composed of all 
western white wheat fit for warehousing, weighing not less than 54 
pounds to the measured bushel, and not sound enough or otherwise 
fit for the higher grades. 

Rejected Western White Wheat. — Shall comprise all wes- 
tern white wheat fit for warehousing but unfit for higher grades. 

Note. — Western Red Wheat and Western Wheat shall corre- 
spond in all respects with the grades of Nos. 1, 2, 3, and Rejected. 



OATS, BARLEY, RYE, ETC. 285 

DURUM (MACARONI) WHEAT 

No. 1 Durum Wheat. — Shall be bright, sound, dry, well cleaned, 
and be composed of durum commonly known as macaroni wheat 
and weigh not less than 60 pounds to the measured bushel. 

No. 2 Durum Wheat. — Shall be dry, clean, and of good milling 
quality. It shall include all durum wheat that for any reason is 
not suitable for No. 1 Durum and weigh not less than 58 pounds to 
the measured bushel. 

No. 3 Durum Wheat. — Shall include all durum wheat bleached, 
shrunken, or for any cause unfit for No. 2, and weigh not less than 
55 pounds to the measured bushel. 

No. 4 Durum Wheat. — Shall include all durum wheat that is 
badly bleached or for any cause unfit for No. 3. 

MIXED WHEAT 

In case of any appreciable admixture of Durum, Western, Winter 
or Western White and Red Wheat, with Minnesota grades of North- 
ern Spring Wheat, or with each other, it shall be graded according 
to the quality thereof and classed as Nos. 1, 2,3, etc., Mixed Wheat, 
with inspector's notation describing its character. 

CORN 

No. 1 Corn. — Shall be corn of various colors, sound, plump, and 
well cleaned, and shall contain not more than 1 5 per cent of moisture. 

No. 2 Corn. — Shall be corn of various colors, sweet, reasonably 
clean, and shall not contain more than 15! per cent of moisture. 

No. 3 Corn. — Shall be corn of various colors, sweet, shall be 
reasonably sound and reasonably clean, and shall not contain more 
than 19 per cent of moisture. 

No. 4 Corn. — Shall include all corn not wet and not in heating 
condition that is unfit for No. 3 corn. 

YELLOW CORN 

No. 1 Yellow Corn. — Shall be 98 per cent yellow, sweet, 
sound, plump, and well cleaned, and shall contain not more than 
15 per cent of moisture. 

No. 2 Yellow Corn. — Shall be 90 per cent yellow, sweet, shall 



286 AGRICULTURAL CHEMISTRY 

be reasonably clean and shall not contain more than 15! per cent 
of moisture. 

No. 3 Yellow Corn. — Shall be 90 per cent yellow, sweet, 
shall be reasonably clean and reasonably sound, and shall not con- 
tain more than 19 per cent of moisture. 

No. 4 Yellow Corn. — Shall include all yellow corn not wet 
and not in heating condition that is unfit for No. 3 Yellow. 

Note. — Nos. 1, 2, 3, and 4 White Corn shall correspond in all 
respects with the grades of Nos. 1, 2, 3, and 4 Yellow Corn. 



OATS 

No. 1 White Oats. — Shall be white, dry, sweet, sound, clean, 
and free from other grain, and shall weigh not less than 3 2 pounds 
to the measured bushel. 

No. 2 White Oats. — Shall be seven eighths white, dry, sweet, 
sound, reasonably clean, and practically free from other grain, and 
shall weigh not less than 31 pounds to the measured bushel. 

No. 3 White Oats. — Shall be seven eighths white, dry, sweet, 
sound, reasonably clean, and practically free from other grain, and 
shall weigh not less than 28 pounds to the measured bushel. 

No. 4 White Oats. — Shall include all oats not sufficiently sound 
and clean for No. 3 White Oats and shall weigh not less than 24 
pounds to the measured bushel. 

Yellow Oats. — The grades of Nos. 1, 2, and 3 Yellow Oats 
shall correspond with the grades of Nos. 1, 2, and 3 White Oats, 
excepting that they shall be of the yellow varieties. 

No. 1 Oats. — Shall be dry, sweet, sound, clean, and free from 
other grain, and shall weigh not less than 32 pounds to the meas- 
ured bushel. 

No. 2 Oats. — Shall be dry, sweet, sound, reasonably clean, and 
practically free from other grain and shall weigh not less than 31 
pounds to the measured bushel. 

No. 3 Oats. — Shall be all oats that are merchantable and ware- 
houseable, and not fit for the higher grades. 

No. 1 Clipped White Oats. — Shall be white, dry, sweet, sound, 
clean, and free from other grain, and shall weigh not less than 40 
pounds to the measured bushel. 

No. 2 Clipped White Oats. — Shall be seven eighths white, dry, 



OATS, BARLEY, RYE, ETC. 287 

sweet, sound, reasonably clean, and practically free from other 
grain, and shall weigh not less than 38 pounds to the measured 
bushel. 

No. 3 Clipped White Oats. — Shall be seven eighths white, 
dry, sweet, sound, reasonably clean, and practically free from other 
grain, and shall weigh not less than 36 pounds to the measured 
bushel. 

RYE 

No. 1 Rye. — Shall be sound, plump, and well cleaned, and 
shall weigh not less than 56 pounds to the measured bushel. 

No. 2 Rye. — Shall be sound, reasonably clean and reasonably 
free from other grain, and shall weigh not less than 54 pounds to 
the measured bushel. 

No. 3 Rye. — All rye slightly damaged or from any other cause 
unfit for No. 2 shall be graded No. 3. 

BARLEY 

No. 1 Barley. — Shall be plump, bright, clean, and free from 
other grain, and shall weigh not less than 48 pounds to the measured 
bushel. 

No. 2 Barley. — Shall be sound and of healthy color, not plump 
enough for No. 1, reasonably clean and reasonably free from other 
grain, and shall weigh not less than 46 pounds to the measured 
bushel. 

No. 3 Barley. — Shall include all slightly shrunken and other- 
wise slightly damaged barley, not good enough for No. 2, and shall 
weigh not less than 44 pounds to the measured bushel. 

No. 4 Barley. — Shall include all barley fit for malting pur- 
poses, not good enough for No. 3. 

No. 1 Feed Barley. — Must test not less than 40 pounds to the 
measured bushel and be reasonably sound and reasonably clean. 

No. 2 Feed Barley. — Shall include all barley which is for any 
cause unfit for the grade of No. 1 Feed Barley. 

Chevalier Barley. — Nos. 1, 2, and 3 Chevalier Barley shall 
conform in all respects to the grades of Nos. 1,2, and 3 Barley except 
that they shall be of a chevalier variety, grown in Montana, Oregon, 
and on the Pacific coast. 



288 AGRICULTURAL CHEMISTRY 

No Grade. — All Wheat, Barley, Oats, Rye, and Corn in a heat- 
ing condition, too musty or too damp to be safe for warehousing or 
that is badly bin burnt, or fire burnt, badly damaged, exceedingly 
dirty, or otherwise unfit for store, shall be classed as No Grade, 
with inspector's notation as to quality and condition. 

SPELTZ 

No. i Speltz. — Shall be white, dry, sweet, sound, clean, and 
free from other grain, and shall weigh not less than 37 pounds to 
the measured bushel. 

No. 2 Speltz. — Shall be dry, sweet, sound reasonably clean, and 
practically free from other grain, and shall weigh not less than 36 
pounds to the measured bushel. 

No. 3 Speltz. — Shall be all speltz that are merchantable and 
warehouseable, and not fit for the higher grades. 

FLAXSEED 

No. 1 Northwestern Flaxseed. — Shall be mature, sound, dry, 
and sweet. It shall be northern grown. The maximum quantity 
of field stack, storage or other damaged seed intermixed shall not 
exceed twelve and one half (12I) per cent. The minimum weight 
shall be fifty-one (51) pounds to the measured bushel of commer- 
cially pure seed. 

No. 1 Flaxseed. — Shall be northern grown, sound, dry, and free 
from mustiness, and carrying not more than twenty (20) per cent 
of immature or field stack, storage, or other damaged flaxseed, and 
weighing not less than forty-nine (49) pounds to the measured 
bushel of commercially pure seed. 

No. 2 Flaxseed. — Flaxseed that is bin burnt, immature, field 
damaged or musty, and yet not to a degree to be unfit for storage, 
and having a test weight of not less than forty-seven (47) pounds 
to the measured bushel of commercially pure seed, shall be No. 2 
Flaxseed. 

No Grade Flaxseed. — Flaxseed that is damp, warm, moldy, 
fire burnt, very musty, or otherwise unfit for storage, or having a 
weight of less than forty-seven (4 7) pounds to the measured bushel 
of commercially pure seed, shall be No Grade. 



OATS, BARLEY, RYE, ETC. 289 

The following abbreviations to be used by inspectors in desig- 
nating the grades : 

R. Wt. for Red Winter 

O. for Northern 

H. for Hard 

Wn. W. for Western White 

Wn. R. for Western Red 

W. for Winter 

W. Wt. for ' White Winter 

Mx. for Mixed 

Y. Corn for Yellow Corn 

W. Corn for White Corn 

N. G. for No Grade 

Bly. for Barley 

Fd. for Feed 

Du. for Durum 

Rej. for Rejected 

MANNER OF TESTING 

Wheat, Flax, and Rye shall be tested after cleaning. The test 
kettle shall be placed where it cannot be jarred or shaken. From 
scoop, bag, or pan, held two inches from top of kettle, pour into 
middle of same at a moderate speed, until running over, strik- 
ing off in a zigzag manner with the edge of beam held horizontally. 

Note. — No grains shall in any case be graded above that of the 
poorest quality found in that lot when it bears evidence of being 
plugged or doctored. 

Note. — Wheat scoured or otherwise manipulated, the test 
weight will not be considered in grading same. 

Note. — The grades of "Purified Oats" or "Purified Barley" 
shall correspond with the other grades of Oats and Barley, except 
that same shall be designated as "Purified." 

Grades are subject to change according to the character of the 
crops as influenced by climatic conditions. Wheat that grades No. 1 
Northern one year might be assigned either a higher or a lower 
grade another year. Grades are relative rather than absolute. 



290 



AGRICULTURAL CHEMISTRY 



Composition of Grains and Seeds. 
(From Jenkins and Winton.) 



Crude Ether 

Water. protein. extract. 

Per cent. Per cent. Per cent. 

Corn, dent 10.6 10.3 5.0 

Corn, dent (max.). . . 19.4 12.8 7.5 

Corn, dent (min.) . . . 6.2 7.5 3.1 

Corn, flint 11.3 10.5 5.0 

Corn, sweet 8.8 11.6 8.1 

Oats 11. o 11. 8 5.0 

Barley 10.9 12.4 1.8 

Rye 11. 6 10.6 1.7 

Rice 12.4 7.4 0.4 

Buckwheat 10.9 10.5 5.4 

Peas 1 10. 1 21.6 1.0 

Flaxseed 1 5.1 27.5 38.6 

Millet seed 1 12.5 10.6 3.9 

Navy beans 12.4 22.2 1.4 

1 Minnesota analyses. 



Nitrogen- 






free ex- 


Crude 


Ash. 


tract. 


fiber. 


Per 


Per cent. 


Per cent. 


cent. 


70.4 


2.2 


1.5 


75-7 


4-8 


2.6 


65-4 


O.9 


1.0 


70.1 


1-7 


1.4 


66.8 


2.8 


1.9 


59-7 


9-5 


3-o 


69.8 


2.7 


2.4 


72.5 


1-7 


1.9 


79.2 


0.2 


0.4 


69.6 


2.1 


i-5 


58.2 


5-7 


3-4 


17.9 


7-4 


3-5 


61. 1 


8.1 


3-8 


53-i 


7.2 


3-7 



CHAPTER XXXII 
Mill and By-products 

410. Sources. — Various by-products are obtained in 
the milling of wheat and in the preparation of cereal 
foods, malting of grain, extraction of oil from seeds, and 
manufacture of starch and glucose, and these are used 
for the feeding of animals. 

411. Wheat By-products. — In the milling of wheat, 
about 72 per cent of the grain is returned as straight 
grade or patent flour, .5 per cent as low grade, 1.50 per cent 
red-dog or feeding flour, and 25 per cent as wheat offal — 
bran, shorts, or middlings. The mechanical losses and 
shrinkage due to drying amount to about 1 per cent. 
The separation of the wheat kernel into these various 
products is a mechanical operation effected by rolls for 
the reduction of the grain, and sieves and bolting cloths 
for the separation of the various products. The grades 
of flour and the percentage amounts of by-products 
recovered in milling vary with the character of wheat 
used and the individuality of the mill. (See Section 385.) 

412. Wheat Bran is composed mainly of the outer 
layers of the wheat kernel removed in the manufacture of 
flour. Some of the floury portion and aleurone cells 
find their way into the bran and fine bran or shorts. 
Wheat bran varies in chemical composition and feeding 
value according to the composition and character of the 
wheat used and the process of milling. It may contain 
as low as 14 and as high as 18 per cent of crude protein ; 

291 



292 AGRICULTURAL CHEMISTRY 

average bran contains about 15 per cent. Two samples 
of bran may have about the same percentage amount of 
protein and not have the same feeding value. For example, 
one wheat containing 13 per cent protein may be exhaus- 
tively milled and yield a bran of 1 5 per cent protein, while 
another wheat with 15J per cent imperfectly milled may 
yield bran with 16 per cent protein. While both brans 
contain nearly the same amount of crude protein, the 
second sample would have more available non-nitrogenous 
nutrients and with the same per cent of crude protein 
would produce better results in feeding than the first 
sample. There is usually more protein in spring wheat 
bran than in winter wheat bran. This is due largely to 
the more nitrogenous character of the spring wheat. 
Bran should be practically free from weed seeds and all 
foreign matter. 

Bran occupies a high position among animal foodstuffs. 
It is bulky in nature and can be fed in comparatively 
large amounts without injury to animals. Director 
Henry in " Feeds and Feeding " states : " Next to corn, 
wheat bran is the great cow feed of this country. Rich 
in ash and protein, carrying a fair amount of starchy 
matter, its light, chaffy character renders it the natural 
complement of heavy corn meal. Though its nutritive 
constituents approximate those of cottonseed meal, it 
mixes well with that feed, causing it to lie more lightly 
in the stomach. 

" The large amount of mineral matter in bran is another 
factor of much importance in milk production. In milk 
there is much mineral matter, placed there for the frame- 
work of the calf, and bran supplies this more abundantly 
than most feeding stuffs. 

" Middlings, like bran, are extensively fed to dairy 



MILL AND BY-PRODUCTS 293 

cows. Being themselves heavy in character, they do not 
mix well with heavy feeds like cottonseed meal and corn 
meal. Dairymen will find middlings much relished by 
cows and yielding satisfactory returns. Bran and mid- 
dlings are conceded by all who have fed them to favorably 
affect the flow of milk. Cows may be fed as much as 6 
to 8 pounds of bran daily and from 4 to 6 pounds of 
middlings. Bran was at first regarded with favor only by 
dairymen. Gradually the steer feeder is learning, its 
value in connection with other grain in the feed box. 
Because of its bulky character and its cooling, slightly 
laxative properties, bran is a most excellent dilutent for 
corn meal, cottonseed meal, and other heavy food sub- 
stances. Where it can be obtained at a reasonable price, 
the stockman will find much satisfaction in mixing one 
third its weight of bran with cornmeal." 

In commenting upon the feeding value of wheat by- 
products, Jordan, in the " Feeding of Animals," states : 
" No commercial feeding stuffs are regarded with greater 
favor, or are more widely and largely purchased by Amer- 
ican feeders than the by-products from milling wheat. 
Wheat bran and middlings are cattle foods of standard 
excellence, whether we consider composition, palatable- 
ness or their relation to the quality of dairy prod- 
ucts." 

413. Wheat Shorts or Middlings consist of those outer 
portions of the wheat kernel which contain somewhat 
less crude fiber, protein, and ash than the parts which 
make up the bran. This product is practically the fine 
bran subjected to more complete pulverization and mixed 
with some " floury " stock. It is more variable in com- 
position than bran, but for some purposes, as pig feed- 
ing, is more valuable. 



294 AGRICULTURAL CHEMISTRY 

Standard middlings and flour middlings are products 
with different amounts of " floury " stock. Used in con- 
nection with animal feeding, middlings means an entirely 
different product from the purified middlings mentioned 
in Section 385, which form the basis of the patent grades 
of flour. Wheat germ is a part of the shorts or middlings 
and is rich in both protein and fat. About 6 per cent of 
the wheat offal is germ. It would impart poor keeping 
qualities if present in flour, and its proteids are not suit- 
able for bread-making purposes. 

414. Wheat Feed or Mixed Wheat Feed is composed 
of the bran, shorts, or middlings and the " red-dog " or 
feeding flour in the proportions obtained in the manu- 
facture of flour. It is a mechanical mixture of all of the 
wheat by-products and has a high feeding value. It is 
particularly valuable for milk production, and because 
of its physical composition possesses some advantages 
over bran or middlings fed alone. A mixed wheat feed 
should contain 1 5 per cent or more of protein, 4. 5 per cent 
fat, and less than 9 per cent fiber. 

415. Wheat Screenings are a mixture of various seeds 
with occasionally broken and shrunken wheat kernels, 
and vary in composition and food value with the different 
kinds of weed seeds present. They should be finely 
ground so as to prevent the introduction of foul weeds 
on the farm. During recent years, mustard seeds have 
been removed from wheat screenings and sold as a separate 
product, the oil which they contain being extracted and 
used commercially. 

416. Linseed Meal. — When the oil is extracted from 
flaxseed, linseed cake is obtained which, when ground, 
forms linseed meal. Linseed meal should contain 35 
per cent crude protein. The darker-colored meals are 



MILL AND BY-PRODUCTS 295 

those which contain most oil. Linseed meal is a con- 
centrated nitrogenous animal food and is valuable for 
feeding all kinds of farm animals. It should be combined 
with other foods. Linseed meal is occasionally adulterated 
with flax screenings. Hence, if adulteration is suspected, 
the cake itself may be purchased and ground. The cake 
is not adulterated because weed seeds and impurities 
must be removed in order to produce a good quality of 
oil. When the oil is removed from the flaxseed by naphtha 
and other chemicals, the product is called "new process 
linseed meal," which differs from pressure process meal 
by having the oil more thoroughly extracted and by con- 
taining a larger amount of crude protein. There is but 
little new process meal found on the market. 

417. Cottonseed Cake and Meal, obtained from cotton- 
seed after removal of the hulls and extraction of the 
oil, are concentrated nitrogenous foods. The meal is 
lemon-yellow in color and is characteristically rich in 
crude protein and ether extract. It contains somewhat 
more crude protein than linseed meal. Cottonseed meal 
is a concentrated nitrogenous food and can be fed, when 
properly combined with other foods, to sheep and beef 
and dairy animals. It cannot safely be fed in large 
amounts nor for a long period to swine. When used in 
a dairy ration as the principal food, it influences the 
character of the butter fat, producing butter with a 
high melting point. 

418. Oat Feed is a product obtained in the manufacture 
of oatmeal. It is variable in composition and consists of 
light-weight oats mixed with oat clippings. Oat hulls 
have about the same composition and feeding value as 
oat straw, and are frequently used for the adulteration of 
animal foods. In the purchase and use of oat feeds, 



296 AGRICULTURAL CHEMISTRY 

particular attention should be given to their composition. 
High-grade oat feed is valuable, but when it contains 
any appreciable amount of hulls, the food value is propor- 
tionally lessened. 

419. Gluten Meal is a by-product obtained in the manu- 
facture of glucose. Soaked corn is broken open and the 
germ is liberated and floated off with water. The oil 
from the germ is extracted and the germ cake sold as a 
commercial product or used for mixing with other foods. 
The starch and gluten of the corn are separated by me- 
chanical means. The starch being heavier separates and 
settles. The gluten product is dried, ground, and sold 
as gluten meal, which usually has about 35 per cent of 
protein and 3 per cent of fat. Gluten feed contains the 
corn hulls or bran along with the gluten meal. The 
hulls reduce the proportion of protein. Gluten feed 
usually contains about 25 per cent of crude protein, but 
is variable in composition. 

420. Malt Sprouts. — When barley is subjected to the 
malting process, germination takes place, which results 
in changing the starch to maltose. The plantlets or 
sprouts are removed, dried, and sold as malt sprouts. 
They are nitrogenous in character and contain about 
22 per cent of crude protein, the larger portion of which 
is in soluble form. Malt sprouts are valuable for feeding 
sheep and beef and dairy stock. 

421. Miscellaneous By-products. — There are a large 
number of miscellaneous by-products used for feeding 
animals as rye bran, buckwheat middlings, palm-nut meal, 
hominy chops, etc. Their composition and general feed- 
ing value may be noted from the table of analyses at 
the close of the chapter. 

422. Inspection of Feeding Stuffs. — During recent 



MILL AND BY-PRODUCTS 



297 



years, many of the states have passed laws regulating the 
inspection and sale of animal feeding stuffs. The object 
of such laws is to prevent adulteration of animal foods by 
requiring manufacturers and dealers to guarantee the 
percentage amounts of crude protein and fat. Many of 
the European countries have had such laws in force for a 
number of years. It is noticeable that in those countries 
and states where feeding stuffs are subjected to inspec- 
tion, the quality is better than where they are not in- 
spected. The national pure food law is applicable to 
animal foods in that it requires all foods to properly corre- 
spond with their labels so that the purchaser may know 
what he buys. 

Experiment 73. — Graphic composition of foods. Make a draw- 
ing of some human or animal food material and indicate graphically 
the percentage amount of the different nutrients. If a hundred 
millimeter rule is used in the construction of the drawing, each 




t " 'a 0" o "2, «,<^ 

I t STARCH CTC 0) 

/ a « " e *Oe<» %"l 



*.*"> 



» o 



U 5 



.»,», 



B 










"ARCH [ICo. 



J.-0 



&'^ 



I 



751 o °h> 




\^ '* *« *i *fe> » "«,' 
' °* o r '°J t» *«0 
•1 "starch etc }oJ 
V " v 6 a ° * 






WHEAT FLOUR. 


CORN MEAL 


OAT MEAL 




■ .FAT 8 


1 FAT M 






1 ASH ♦ 


i ASH > 







Fig. 91. — Graphic composition of foods. 



linear millimeter will correspond to 1 per cent. If a food contains 
12 per cent water, 12 millimeters are measured off to represent the 
water in the material, and so for each class of nutrients an area 
corresponding to its percentage amount. 



298 AGRICULTURAL CHEMISTRY 

Composition of Mill and By-products. 



£ < 

Per Per 

cent. cent. 

Linseed meal (old process) . . 9.20 5.70 

Linseed meal (new process) . 10.10 5.80 

Cottonseed meal 8.20 7.20 

Malt sprouts 10.20 5.70 

Corn and cob meal 15.10 1.50 

Gluten meal 9.60 0.70 

Gulten feed 7.80 1.10 

Oat feed 7-7° 3-7© 

Oat hulls 7-30 6.70 

Sugar-beet pulp l 88.53 4-^5 

Rye bran 11.60 3.60 

Buckwheat middlings 13.20 4.80 

Palm-nut meal 8.30 3.70 

Hominy chops 11. 10 2.50 

Apple pomace 76.70 0.50 

Wheat feed 12.00 4.00 

Wheat feeding flour (red 

dog) 1 2.00 3.00 

Wheat bran, winter 12.30 5.90 

Wheat bran, spring n.5° 5-4Q 

Wheat shorts 11.80 4.60 

Wheat screenings 11.60 2.90 

Meat scrap 1.33 8.03 

Wheat flour (Minn.) 11.90 0.40 

Corn meal 15.10 1.40 

Corn flour 12.57 0.61 

Buckwheat flour 14.60 1.00 

Oatmeal 7-9° 2.00 

1 Dry matter basis 



a *s 



"53 


|4 


3 <u 


6a0 « 
O V 


4J 


Per 


Per 


Per 


Per 


cent. 


cent. 


cent. 


cent. 


32.90 


8.90 


35-40 


7.90 


33-20 


9-50 


38.40 


3.00 


42.30 


5.60 


23.60 


13.IO 


23.20 


IO.70 


48.50 


I.70 


8.50 


6.60 


64.80 


3-50 


29.40 


I.60 


52.40 


6.30 


24.OO 


5.30 


51.20 


IO.60 


16.OO 


6.IO 


59-40 


7.IO 


3-3° 


29.70 


52.10 


I. OO 


9-45 


22.40 


62.62 


O.68 


14.70 


3.50 


63.80 


2.8o 


28.90 


4.IO 


41.90 


7.IO 


14.40 


21.40 


38.90 


I3-30 


9.80 


3.80 


64.50 


8.30 


I.40 


3-90 


16.20 


I.30 


16.OO 


8.00 


55-°o 


5.00 


17.OO 


3.00 


59.00 


6.00 


16.OO 


8.IO 


53-7o 


4.00 


16.IO 


8.00 


54-50 


4-50 


14.90 


7.40 


56.80 


4-50 


12.50 


4.90 


65.10 


3.00 


57.69 






32.95 


I2.6o 




74.30 


O.80 


9.20 


I.90 


68.70 


3.80 


7-13 


O.87 


78.36 


1-33 


6.90 


O.30 


75.80 


I.40 


14.70 


O.90 


67.40 


7-IO 



CHAPTER XXXIII 
Roots, Tubers, and Fruits 

423. General Composition. — Roots, tubers, and fruits 
contain much water and but little dry matter. The dry 
matter is mainly non-nitrogenous compounds, as starch 
and sugar. All contain some nitrogenous compounds, of 
which the larger portion are amides and non-proteid 
forms. Mineral forms of nitrogen, as traces of nitrates 
and nitrites, are usually present. Organic acids in small 
amounts and essential oils are characteristic features. 

424. Potatoes contain about 75 per cent of water. 
The dry matter is largely starch. About half of the 
nitrogen is present as proteids, of which the larger portion 




SI Protein. El Pat ■ Indigestible. 

Fig. 92. — Composition of potatoes. 

is in the form of soluble albumin. The amount of fat is 
small, less than one tenth of one per cent. Potatoes 
contain tartaric and other organic acids, pectose sub- 
stances, and other compounds in small amounts, and little 

299 



3°° 



AGRICULTURAL CHEMISTRY 



cellulose. When potatoes are stored for any length of 
time and fermentation takes place, a portion of the starch 
is converted into glucose. In storing them, a low tem- 
perature and good ventilation are necessary to prevent 
fermentation. Potatoes are a concentrated, non-nitroge- 
nous food. 

425. Carrots contain approximately the same amount 
of water as milk, viz., 87 per cent, and about half as 
much dry matter as potatoes. The 12 per 
cent of dry matter is nearly half sugar, 3 
per cent being fruit sugar and 3 per cent 
other sugars. There is 1.20 per cent of total 
nitrogenous compounds given as crude pro- 
tein in tables of analyses, of which 40 per cent 
is protein. Carrots contain more fat than 
potatoes. 

426. Parsnips contain more dry matter 
than carrots and have nearly the same 
amounts of nitrogenous compounds, fat, and 
fiber, but less sugar and more starch. They 
have about the same general food value as 
carrots. 

427. Mangel wurzels have more water 
and less dry matter than carrots. The 
dry matter, however, is richer in nitrogenous 
compounds than that of carrots, parsnips, 
potatoes, or beets, which makes the mangels 
a better balanced food. The 10 per cent 
of dry matter is a little more than half 

starch, and contains about 1.40 per cent of crude protein, 

of which half is protein. Mangels also contain about 1 

per cent each of ash and fiber and a small amount of fat. 

428. Apples vary in composition with the variety and 




I.FIBER. STARCH, 

FAT ETC. 
2.SUGAR 
J.PROTEIN+NI- 

TROGENOUS MAT 

TER. 
4.ASH. 

Fig. 93. — Com- 
position of 
carrots. 



ROOTS, TUBERS, AND FRUITS 3OI 

physical characteristics. They contain from 10 to 16 per 
cent solids, of which 75 per cent is sugar or allied carbo- 
hydrates, and about half a per cent each is fat and protein. 
Among the organic acids, malic predominates. The 
flavor and special characteristics depend upon the relative 
amounts of the different sugars, as sucrose, levulose, and 
dextrose, and the organic acids and essential oils which 
the apples contain. It is these compounds which give 
individuality to apples. 

429. Oranges contain from 10 to 15 per cent of solid 
matter, the larger portion, 80 per cent, being sugar. The 
citric acid content ranges from 1 to 2.5 per cent in dif- 
ferent varieties. The amounts of protein, fat, and fiber 
are small. The ash or mineral matter averages about 
one half per cent, and is composed mainly of potash and 
lime with smaller amounts of other compounds. The 
iron and sulfur content is generally larger than is ordinarily 
found in fruits. The physical composition of average 
oranges is as follows : rind, 20 to 30 per cent ; pulp, 
25 to 35 per cent ; and juice, 35 to 50 per cent. 

430. Lemons differ from oranges in containing more 
citric acid and less sucrose, levulose, and dextrose. The 
average composition of lemons is as follows : 

Physical Composition. Chemical Composition. 

Per cent. Per cent. 

Rind 25 to 35 Solids 10 to 12 

Pulp 25 to 35 Sugar 2 to 4 

Juice 40 to 55 Citric acid 6 to 9 

The ash of the lemon is somewhat similar in composi- 
tion to that of the orange, but is present in larger amount. 

431. Strawberries are characterized by containing a 
high per cent of water, 90 to 92 per cent. Sugar and 



302 AGRICULTURAL CHEMISTRY 

malic acid are the materials present in largest amounts, 
while protein, fat, ash, fiber, coloring materials, and 
essential oils form but a small part of the composition. 
While strawberries are valuable as a food adjunct, they 
do not supply any appreciable amount of nutrients. It 
has been estimated that it would require 13 pounds of 
strawberries to furnish the carbohydrates needed for a 
daily ration, to say nothing of the protein, which would 
require 65 pounds additional. The malic and other 
acids are valuable because of their antiseptic properties 
which, added to the appearance and palatability, make 
strawberries a valuable food adjunct. 

432. Grapes vary in composition according to variety. 
They contain from 15 to 20 per cent of solid matter. 
In the juice is from 10 to 15 per cent or more of sugar 
in the form of sucrose, levulose, and glucose. Tartaric 
acid is found in grapes more liberally than in other fruits, 
and ranges from 1 to 1.5 per cent. There is very little 
fat and protein, and while grapes add some nutrients, as 
sugar, to a ration, they do not contribute any large 
amount. There is some food value, but it is not so high as 
is occasionally claimed for them. Their value, as is the 
case with other fruits, is in palatability, and indirectly 
aiding in digestion, and thus adding value to other foods. 

433. Olives, when fully matured and fresh, contain 
about 15 per cent of oil. When preserved green, there is 
considerably less. Olives also contain small amounts of 
other compounds and essential oils. Pure olive oil is a 
valuable food, but it is frequently adulterated with refined 
cottonseed and other vegetable oils. Olive oil is slightly 
laxative in character and assists mechanically in the 
digestion of foods by preventing compaction of feces in 
the intestines. 



ROOTS, TUBERS, AND FRUITS 303 

434. Dried Fruit. — Many fruits are preserved by 
drying. Dried fruit has a somewhat different composi- 
tion from fresh fruit because of chemical changes which 
occur during the drying process and the slight loss of 
volatile and essential oils. Dried fruits, when free from 
objectionable preservative agents, are valuable, and can be 
used to advantage when fresh fruits are not obtainable. 

435. Miscellaneous Fruits. — Since the list of fruits 
that could be discussed is large, only a few examples 
have been considered. For additional information upon 
the subject, or for data upon fruits not given, the student 
is referred to the bulletins of the California Experiment 
Station. 

436. Food Value. — If judged entirely on the basis of 
nutrients, many vegetables and fruits would be assigned 
a low place in the list of foods, as they contain compara- 
tively small amounts. Most fruits are used in the dietary 
not so much with the view of supplying nutrients as for 
other purposes. The organic acids, essential oils, and 
soluble mineral compounds, together with the digestible 
form in which the nutrients are present, are factors which 
give fruits their unique value. The organic acids and 
essential oils impart palatability and assist functionally 
in the digestive process. Some fruits, as figs and prunes, 
contain chemical compounds which are laxative in char- 
acter. In the human ration, fresh fruits are as essential, 
and occupy the same position, as roots and vegetables in 
animal rations. 



CHAPTER XXXIV 
Fermentation 

437. Insoluble Ferments. — Fermentation is a chemical 
change produced by a class of bodies called ferments. 
Insoluble or organized ferments are single-celled, micro- 
scopic plants which have a definite structure. Many of 
them are bacteria, low forms of plant life. Nearly all 
secrete definite chemical products capable of producing 
fermentation. The insoluble or organized ferments are 
composed mainly of nitrogenous compounds, but they 
also contain non-nitrogenous and mineral matter. Some, 
as the tubercular organism, contain cellulose. 

438. Soluble Ferments or Enzymes. — Enzymes are 
organic compounds, secreted by cells, and have the 
ability to produce chemical changes. They are also 
called soluble ferments, and chemical ferments. There 
are a great many different kinds of soluble ferments, 
some of which, as diastase and maltase, act upon car- 
bohydrates, while others, as pepsin and pancreatin, act 
upon proteid bodies. Enzymes produce chemical change 
without entering into the composition of the substance 
or giving up any of their own material to the reacting 
compounds. A small amount of diastase will change 
a large amount of starch to soluble forms without losing 
its power of action. The enzymes are all soluble in water 
and are precipitated with strong alcohol. Their action 
is not generally retarded by antiseptics and chemicals 

3°4 



FERMENTATION 305 

which are capable of destroying organized ferments. 
When seeds are soaked in water, the diastase and proteose 
enzymes are extracted, and if precipitated with alcohol 
and recovered, they appear as a light gray powder. An 
organized ferment is a low form of plant, while a soluble 
ferment is a chemical product. 

439. Aerobic and Anaerobic Ferments. — Ferments 
which require oxygen for their existence are aerobic, 
while those which are capable of working in the absence 
of oxygen are anaerobic. The aerobic ferments produce 
carbon dioxid, water, ammonia, and hydrogen sulfid as 
final products, while the anaerobic ferments usually 
produce intermediate products as organic acids. 

440. Conditions Necessary for Fermentation. — The 
conditions necessary for fermentation are: (i) moisture, 
(2) favorable temperature, (3) a ferment body, and (4) a 
fermentable substance. Moisture is necessary in order 
that the chemical changes may take place. During 
fermentation water frequently enters into the chemical 
reaction, as in hydration changes, and is also necessary 
as a medium of exchange for the chemical products dur- 
ing the reaction. The most favorable temperatures for 
fermentation are between 15 and 6o° C. Below zero and 
above the boiling point of water, ferments are inactive. 
Certain ferments require a different temperature for 
activity than others, and some have greater resistance 
to the action of heat. A ferment body is always necessary 
in order to start the fermentation change, and in the 
absence of a ferment either organized or unorganized, no 
fermentation can take place. A fermentable substance, 
with the right kind of ferment to act upon it, is also 
requisite, as a ferment which acts upon one class of bodies 
is incapable, unaided, of acting upon others ; for example, 



306 AGRICULTURAL CHEMISTRY 

the peptic ferment is incapable of changing starch to 
soluble forms. When a substance is freed from all fer- 
ments and is protected from outside sources of contami- 
nation, it is in a sterile condition. Many forms of fer- 
mentation are produced by the spores of organized 
ferments gaining access to a material along with dust 
particles carried in the air. In the preservation of food, 
a knowledge of the conditions requisite for fermentation 
is made use of. The products formed by ferments are 
numerous, as there are ferment bodies capable of acting 
upon all forms of organic matter. Some of the ferments 
assist in the digestion of food and in the preparation of 
food products, while others take an important part in 
everyday life affairs, and in agriculture, as in the libera- 
tion of plant food. The growth of plants, the preparation 
of foods, their digestion, and the manufacture of food 
products all depend largely upon fermentation. 

441. Soil Ferments. — In the growth of plants, fer- 
ments take an important part, both in the preparation of 
the plant food and in the chemical changes which occur 
within the plant. Disintegration of the mineral food of 
the soil is assisted by ferment action. The nitrogenous 
food of the plant is prepared in the soil by ferments. 
The subject of soil ferments is briefly considered in 
" Soils and Fertilizers." 

442. Ferments in Seeds. — In the seeds of plants, 
particularly matured grains, there are a number of fer- 
ments which take an important part in the process of 
germination. These ferments change the insoluble nitrog- 
enous and non-nitrogenous compounds to soluble forms, 
which are utilized by the young plant as food. If a seed 
were deprived of all of its soluble ferments, it would fail 
to germinate. 



FERMENTATION 307 

Experiment 74. — Action of malt on starch. Crush in a mortar 
twenty malted barley kernels, transfer to a test tube, and add 15 
cc. water. After twenty-four hours, filter off the solution, and add 
it to a flask containing 2 grams of flour and 100 cc. water. Place 
the flask in the desk for twenty-four hours ; then filter off the solu- 
tion and test a portion for starch with iodin, as in Experiment 45. 
Test another portion for glucose with Fehling's solution, as in Ex- 
periment 48. 

Questions. — (1) What is malted barley ? (2) What did the water 
extract from the barley contain ? (3) What effect did this extract 
have upon the flour ? (4) What did the tests with iodin and Fehl- 
ing's solution show ? (5) Would flour treated with water instead 
of malt extract give the same result ? 

443. Ferments in Bread-making. — The yeast plant 
employed in bread-making secretes a number of soluble 
ferments which produce the desired chemical changes. 
The yeast plant requires as food, sugar or other soluble 
carbohydrates, mineral matter rich in phosphates, and 
available nitrogen rich in peptones, which are all present 
in grains. Yeast secretes diastase, alcoholic and acid- 
yielding ferments. The diastase ferment changes the 
starch to soluble forms, the alcoholic ferment produces 
alcohol and carbon dioxid gas, which expand the dough 
and make the bread light, and acid ferments produce 
acids, which combine with the gluten proteids and modify 
their character. In short, bread-making is a series of 
chemical changes induced by soluble ferments. 

Experiment 75. — Alcoholic fermentation. Weigh 10 grams of 
flour into a flask, add 50 cc. water and a small piece of yeast (one 
tenth of a cake). Connect the flask by means of a delivery tube 
with the Woulff bottle containing enough clear lime water to cover 
the end of the tube. Place the flask on a warm sand bath, below 
85 F., for half an hour. Observe the bubbles of gas given off and 
the precipitate formed in the lime water. Do not overheat the 
sand bath. 



308 AGRICULTURAL CHEMISTRY 

Questions. — (i) What is yeast arid what does it contain? 
(2) What caused the gas to be given off ? (3) From what was the 
gas formed ? (4) Write the reaction with Ca(OH) 2 . (5) What be- 
comes of the alcohol ? 

444. Ferment Action and Food Digestion. — The diges- 
tion of food is carried on largely by the soluble ferments. 
The digestive tract secretes a number of these, which 
act upon the insoluble nutrients and change them to 
soluble forms. In fact, the digestion of food is dependent 
upon the action of the different ferments in the digestive 
tract, as ptyalin in the saliva, pepsin in the stomach, 
pancreatin in the duodenum, and diastase and other 
ferments in the intestines. 

445. Ferments and Food Preservation. — Preservation 
of food is dependent upon prevention of ferment action. 
The low temperature of cold storage is unfavorable to 
the development of ferments. Sterilization is likewise 
unfavorable. By means of heat, cold storage, chemicals, 
and protection from the spores in the air, perishable food 
products are preserved. Some ferments, however, are 
not destroyed by either high or low temperatures. 

446. Ferments in Butter- and Cheese-making. — The 
processes of butter- and cheese-making are carried on with 
the aid of ferments. Milk contains enzymes or soluble 
ferments and, to a limited extent, is itself capable of 
acting as a digestive fluid. The ripening of cream is 
the result of the action of the lactic acid ferment which 
changes the lactose (milk sugar) into lactic acid. In 
cheese-making, the rennet used for coagulating the milk 
contains a number of ferments which take an important 
part in the process. The flavor and odor of butter as 
well as of cheese are the results of ferment action. In 
butter- and cheese-making, it is the object to control the 



FERMENTATION 309 

action of the desirable ferments and to prevent the unde- 
sirable ones from developing. Ropy milk, red spots in 
cheese, and floating curds in cheese-making are all 
caused by fermentation. Butyric acid, one of the products 
found in foul milk and butter, is caused by the butyric 
acid ferment. Milk is exceedingly susceptible to the 
action of ferments. 

Experiment 76. — Lactic fermentation. Place 5 grams milk 
sugar, 100 cc. water, 5 cc. skim milk, and two or three crystals of 
sodium phosphate in a flask. Leave the flask uncorked in the desk 
for twenty-four hours. Then add a few drops of phenolphthalein 
indicator, and determine the amount of lactic acid. 1 cc. alkali = 
0.000 gram acid. 

Questions. — (1) Why was milk used in this experiment ? (2) What 
was produced from the milk sugar? (3) Why was sodium phos- 
phate used ? (4) How much acid was produced ? 

447. Disease-producing Organisms. — Many diseases 
are caused by the action of microorganisms. The 
disease-producing organisms or bacteria invade the body 
and rapidly multiply, living upon the fluids and tissues 
of the body and producing poisonous products. Typhoid 
fever, smallpox, diphtheria, tuberculosis, cholera, and 
many other diseases are caused by specific bacteria. The 
products resulting from the action of the organism are 
poisonous, and death is often caused by these toxic bodies, 
and sometimes by the organisms' action upon the body 
tissues. The chemical products of organisms, when 
they accumulate, destroy the bodies which produce 
them, hence in combating some diseases these products, 
known as antitoxins, are used. Modern methods of 
sanitation are based upon the destruction of disease- 
producing organisms. 

448. Beneficial Organisms. — While many diseases are 



3IO AGRICULTURAL CHEMISTRY 

caused by microorganisms, not all microorganisms or 
bacteria are injurious. In nearly all foods there are 
large numbers of bacteria which are of a harmless nature. 
Some are valuable and beneficial to man, particularly 
those which assist in plant nutrition and in the preparation 
and digestion of foods. 



CHAPTER XXXV 
Chemistry of Digestion and Nutrition 

449. Digestion, a Biochemical Process. — In the diges- 
tion of food, the enzymes or soluble ferments take an 
important part. Although digestion is not well under- 
stood, it is known to be largely a chemical process brought 
about by ferment action, and hence is called a biochemical 
process. The cells in the different parts of the digestive 
tract secrete chemical products which produce chemical 
changes in the food, rendering it soluble so that the 
various nutrients can be absorbed and used by the body. 
Any compound which is capable of undergoing digestion 
and being utilized for food purposes is called a nutrient. 
The value of any food depends upon the kinds and amounts 
of its nutrients. During the process of digestion, a 
complex series of chemical changes take place, and as a 
result of digestion and of assimilation of food by the 
body, heat and energy are produced. 

450. Digestion Experiments. — The digestibility of a 
food is determined by a digestion experiment. The 
percentage amount of a nutrient which is digested is 
called the coefficient of digestibility. Not all of the 
nutrients in foods are alike digestible. In clover hay, for 
example, 65 per cent of the organic matter is digested, 
while only 30 per cent of the crude fiber and 70 per cent 
of the nitrogen-free extract compounds are digested. 
Each compound has its own digestion coefficient. In 
order to determine the digestibility of a food, an animal 

3" 



312 AGRICULTURAL CHEMISTRY 

is fed, for a number of days, a weighed amount of food 
which is analyzed. All of the feces or solid excrements 
produced during the experimental period are collected, 
weighed, and analyzed. After the food has undergone 
the process of digestion, the undigested portions, along 
with a small amount of digested products, are excreted 
as feces, while the liquid wastes of the body contain the 
products of the digested food. From the weight of the 
food consumed, and its analysis, the amount of each 
class of nutrients consumed is determined. From the 
dry matter of the feces, the undigested nutrients are 
likewise determined. The undigested nutrients sub- 
tracted from the total nutrients in the food consumed 
give the amounts digested, which are calculated on a 
percentage basis. In the case of clover hay, an animal 
may consume 28 pounds per day, containing 12 per cent 
protein; this is equivalent to 3.36 pounds of protein 
(2S X 0.12 = 3.36). An account is opened with the 
animal, in which a charge for t,.t, pounds of protein is 
entered. From the 2S pounds of food, 40 pounds of feces 
or excrements are obtained, as a large amount of water 
is added during the process of digestion. The feces, 
which are composed largely of the indigestible portions 
of the food, are analyzed and found to contain 20 per cent 
of dry matter ; this is equivalent to S pounds of indiges- 
tible matter yielded by the 28 pounds of clover (40 X 0.20 
= 8). The dry matter is analyzed and found to contain 
15 per cent of the protein ; this is equivalent to 1.2 pounds 
of protein (8 X 0.15 = 1.2). The animal is charged 
with 3.36 pounds of total protein; 1.2 pounds are found 
to be indigestible, leaving a balance of 2.16 pounds of 
digestible protein, equivalent to 64 per cent of the total 
(2.16 -f- 3.36 X 100 = 64). Sixty-four is the digestion 



DIGESTION" AND NUTRITION 313 

coefficient of the crude protein in this clover hav. In like 
manner, the digestion coefficients of all the nutrients 
are determined. 

Example. — From the following figures, calculate the digestion 
coefficients of the organic matter, ether extract, crude fiber, and 
nitrogen-free extract of the clover hay. The figures for the com- 
position of clover hay are on the basis of the food as fed, while those 
for the feces are on the basis of the dry matter. 

Composition of Composition of 

Clover. Feces. 

(Hay as fed.) (Dry matter.) 

Water 10.00 

Ash . 6.90 9.50 

Ether extract 3.10 2.10 

Crude protein 12.00 15.00 

Crude fiber 26.00 30.00 

Xitrogen-free extract 42.00 43-4o 

451. Caloric Value of Foods. — During the process of 
digestion, heat is produced in proportion to the calories 
contained in the food and the nutrients digested. By 
the caloric value of a food is meant the amount of heat 
measured in calories which the food yields. A calorie is 
the amount of heat required to raise i kilogram of water 
i° C. or 1 pound of water about 4 F. The caloric value 
of a food is determined by means of the calorimeter 
(Fig. 94). The calorimeter consists of a steel bomb 
in a metal cylinder (0) (Fig. 95) . The bomb is surrounded 
by water as indicated in the illustration, and the cylinder 
containing the bomb and water is placed within a double- 
walled fiber receptacle (T and U). The bomb itself 
consists of three parts : the cylinder, which is lined with 
platinum, the cover, and a collar to hold the cover in 
place and tightly seal the bomb. These three parts of 
the apparatus are shown in Fig. 96. 



314 



AGRICULTURAL CHEMISTRY 



The principle involved in determining the caloric value 
of a food is simple. A weighed amount of the substance 

is burned in the 
calorimeter and 
the rise in tem- 
perature of the 
water that sur- 
rounds the bomb 
is noted. The 
combustion is 
carried on in ox- 
ygen so as to be 
complete, and all 
means possible are 
employed to 
secure accuracy of 
results. The sub- 
stance to be 
burned, if it is a 
material like flour, 
is made into a 
pellet by means 
of a press, so that 
it may form a 
compact mass and 
burn evenly and 
not be scattered 
about in the calo- 
rimeter cylinder 
and be only partially burned. The pellet is placed in the 
small platinum crucible O (Fig. 95). This crucible is sup- 
ported by platinum wires attached to the cover of the calo- 
rimeter. Above the crucible a small coil of fine iron wire 




Fig. 94. — Bomb calorimeter used for determining 
the caloric or heat-producing value of foods. 



DIGESTION AND NUTRITION 



315 



D<£ 



s- 



& 



v//ys///////////s/rs//rs\v///M^^^ 



§S '/SS/S/S/S///S/. fs/ss/rsss/sss/z/yy/* 



W/s/s//s//ss/s/j\ 



VSSSSSSSSSSSA 




Fig. 95. — Bomb calorimeter, showing interior structure and working parts. 
Atwater, Conn. (Storrs) Agr. Expt. Station, Annual Report, 1897. 



316 AGRICULTURAL CHEMISTRY 

is stretched from the platinum wires. The cover is 
screwed tightly upon the cylinder of the bomb and oxygen 
is admitted from an oxygen tank through valve G of 
the cover until a pressure of twenty atmospheres is 
secured, when the valve is securely closed. The bomb, 
with the substance to be burned, and charged with oxygen, 
is placed in the metal cylinder Q, which contains a definite 
amount of water, the temperature of which is carefully 
determined by means of a thermometer that reads to 
0.005 ° C. The water is kept at an even temperature by 
means of the metal stirrer SS, operated by a motor. Con- 
nection is made with a storage battery which ignites 
the small iron wire that is suspended above the substance. 
The burning wire falls upon and ignites the material in 
the platinum crucible O and the heat from the combus- 
tion of the material raises the temperature of the water 
in the calorimeter cylinder. A number of readings are 
taken so as to secure the actual rise in temperature, caused 
by the combustion of the substance. Due allowances are 
made for the heat contributed by the combustion of the 
iron wire, the heat absorbed by the steel bomb, and for 
other factors that are known and under control. 

The approximate amount of energy which' a food will 
yield can be determined by the use of the following factors : 
ether extract 4225, and fiber, nitrogen-free extract, and 
crude protein i860. These are the numbers of calories 
which a pound of each of the nutrients yields. 

452. Available Energy of Foods. — Since only a portion 
of the nutrients of foods is digestible, not all of the total 
caloric value is rendered available to the body. The 
digestion process is more complete with non-nitrogenous 
compounds than with the proteids. The final products 
of oxidation in the case of starch, sugar, and digestible 




Fig 



A BCD E 

96. — Parts of bomb calorimeter and accessories: A, pellet mold; B, cover to bomb; 



C, platinum dish, holding substance burned; D, collar; E, steel bomb — platinum-lined. 



DIGESTION AND NUTRITION 



317 



carbohydrates are carbon dioxid and water. These 
compounds undergo complete combustion. The final 
products of digestion of the proteids are amides, the 
larger portion of which is excreted as 
urea in the liquid waste. This com- 
pound, urea, CH 4 N 2 0, does not undergo 
complete oxidation in the body. If 
burned in the calorimeter, it would 
yield an additional amount of heat. 
The term available energy of a food 
means simply the energy available to the 
body and measured in calories. The 
available energy is obtained by deduct- 
ing from the total digestible energy 
the calories from the residue product, 
as urea, which are not completely 
oxidized. In the determination of the 
available energy of foods, the principle 
is the same as explained in the section 
relating to the digestibility of nutrients. 
The total number of calories in a food 
is determined by the calorimeter ; the 
number of calories in the feces is like- 
wise determined and deducted from 
the total, as well as the caloric value 
of the liquid excrements containing urea. This gives the 
energy of the food which is available to the animal. 

453. Net Energy of Foods. — In the process of diges- 
tion, particularly of coarse fodders which contain much 
crude fiber, energy varying with the density of the tissue 
is required to render the food available to the body. Of 
the total available energy, a portion, and in some cases, 
a large amount, is used in rendering the food available ; 




Fig. 97. — Oxygen 
tank and pressure 
gauge for charging 
the bomb. 



318 AGRICULTURAL CHEMISTRY 

that is, in carrying on the process of digestion. Means 
have been devised whereby the approximate amount of 
work required on the part of the animal to render the 
food available can be determined. When the energy 
used in this way is deducted, it leaves the net energy. 
In the case of coarse fodders, a considerable portion of 
the energy is used in the digestion of the food, leaving, 
in some cases, only comparatively little net energy. Less 
force is required to digest the grains, and thus a larger 
amount of energy is available to the body. A knowledge 
of the total, available, and net energy which different 
foods produce is important, because one of the objects of 
foods is to supply nutrients for the production of energy. 

454. Digestion of Proteids. — The insoluble proteids 
are acted upon by the pepsin ferment secreted by the gas- 
tric juice in the stomach of animals. Peptones are pro- 
duced by this action. Proteids which escape the action 
of the peptic ferment are later brought into contact with 
the tryptic ferment in the pancreas and lower parts of the 
digestive tract. This ferment acts in an alkaline solu- 
tion, while pepsin requires one slightly acid in character. 
The proteids which fail to be digested by either the 
peptic or tryptic ferments are usually expelled as undi- 
gested proteids. In normal digestion, the fluids of the 
stomach are slightly acid, while those of the pancreas and 
intestines are alkaline. For the formation of acids and 
alkalies, sodium chlorid is essential. From this com- 
pound, hydrochloric acid, present in the gastric juice, is 
formed, also the alkaline products in the biliary and other 
fluids. Sodium chlorid is a normal constituent of the 
blood and of many of the vital fluids of the body. 

After serving various purposes in the body, as noted 
in Section 305, the proteids are expelled as amides in 



DIGESTION AND NUTRITION 319 

either the solid or the liquid excrements, the larger portion 
being in the form of urea. From the time the proteids 
are acted upon by the soluble ferments in the digestive 
tract until their products are expelled from the body as 
amides, a large number of intermediate substances are 
formed. Should the proteids fail to undergo normal 
digestion, poisonous products, called ptomaines, are pro- 
duced. 

455- Digestion of the Carbohydrates. — Digestion of 
the carbohydrates begins with the ptyalin ferment of 
the saliva. Carbohydrate digestion takes place mainly 
in the lower part of the digestive tract, where diastase 
and other ferment bodies are secreted which change the 
insoluble carbohydrates to soluble forms. When com- 
pletely digested, carbon dioxid and water are the final 
products. Between the soluble carbohydrates formed by 
the diastase and other ferments, and the final products of 
oxidation, carbon dioxid and water, a large number of 
intermediate products are formed. Glycogen is one of 
these bodies, and is a carbohydrate present in small 
amounts in the blood, but stored up largely in the liver. 
The process of carbohydrate digestion is one in which the 
soluble ferments take an important part, changing the 
insoluble compounds to soluble and assimilable forms. 

456. Digestion of Fats. — Bile and the intestinal fluids 
are the main factors which assist in the digestion of fats. 
After emulsion or separation into fine particles, the fats 
are changed to glycerin and fatty acids by the action of 
a ferment body. They are then absorbed, and undergo 
slow oxidation, whereby carbohydrate-like bodies are 
produced. These products then undergo the same general 
changes as the carbohydrates. 

457. Oxygen Necessary for Digestion. — In order that 



320 AGRICULTURAL CHEMISTRY 

digestion may proceed in a normal way, a liberal supply 
of air is necessary to oxidize the nutrients and to prevent 
the formation of poisonous waste products in the body. 
In the absence of a liberal supply of air, normal digestion 
fails to take place. Oxygen is equally as important as 
protein, fat, carbohydrates, and water. 

458. Factors Influencing Digestion. — There are a 
number of factors which influence the completeness of 
the process of digestion. Some of these factors are : 
(1) mechanical condition of the food, (2) combination 
of foods, (3) amount of food consumed, (4) palatability 
of the food, and (5) individuality of the animal. A 
digestion coefficient is a variable factor capable of being 
influenced by these and other conditions. 

459. Mechanical Conditions. — The mechanical con- 
dition of 'a food, as fineness of division and density of 
particles, materially influences digestion. As a general 
rule, the finer the division, the more complete is the diges- 
tion. For example, experiments with pigs show that 
wheat meal is 10 per cent more digestible than whole 
wheat. Experiments with other animals, recorded in 
Bulletin No. 77, U. S. Department of Agriculture, Office 
of Experiment Stations, giving the digestibility of Ameri- 
can feeding stuffs, show equally large differences. The 
finer the division of the particles, the larger is the surface 
exposed to the action of the digestive fluids. The density 
of a material also influences its digestibility. Many foods 
contain a fair amount of nutrients, but their mechanical 
condition is such that the nutrients are not easily rendered 
available because of the presence of a large amount of 
cellulose inclosing and protecting the nutrients, and as a 
result, digestion and assimilation fail to take place. This 
is particularly true of many coarse fodders, as timothy 



DIGESTION AND NUTRITION 32 1 

hay and clover when allowed to become overripe and 
fibrous. Digestion experiments with such forage, and 
with that cut in early bloom, show that when cut in 
early bloom, it is more digestible than when overripe and 
woody. In the case of human foods also, fineness of 
division of the particles favorably affects the complete- 
ness of the digestion process. Graham or coarsely granu- 
lated flour, although it contains more nutrients, is less 
digestible and furnishes less total available nutrients 
than finely granulated flour. The advisability of grind- 
ing animal foods depends entirely upon the cost of the 
grinding. Where it can be done on the farm at slight 
expense, it invariably pays to grind grains, particularly 
wheat, barley, millet, and others which have a hard seed 
coat. In the feeding of coarse fodders, their mechanical 
condition is an important factor. When shredded corn 
fodder is fed, less energy is required on the part of the 
animal to render the nutrients available. This results in 
the return of a larger amount of net energy from the 
food. 

460. Combination of Foods. — The way in which a 
food is combined and fed in a ration influences its digesti- 
bility. When foods are. fed singly, they are not as com- 
pletely digested as when fed in a well-balanced ration. 
For example, experiments show that corn alone when 
fed to pigs is not as completely digested as when com- 
bined with shorts and other foods. Some foods assist 
in the digestion of other foods. Whenever milk is added 
to the ration for pigs, a larger amount of pork is secured 
than when the same amount of nutrients in other form 
is added. The milk assists in the digestion of the grains 
with which it is combined. Exact experiments to show 
the full extent to which one food influences the digesti- 



322 AGRICULTURAL CHEMISTRY 

bility of another have not as yet been made. In the 
feeding of farm animals, however, the practical results 
which have been obtained show that this is an important 
factor. 

461. Amount of Food Consumed. — In human digestion 
experiments, results show that too large an amount of 
food is not so completely digested as a smaller amount. 
With farm animals, the experiments have not been so 
decisive. In some cases, large rations have been digested 
as completely as smaller ones. This is undoubtedly due 
to individual differences of animals. Excessive amounts 
of foods, however, have a tendency to interfere with 
normal digestion, and the results are not so satisfactory 
as when medium rations are fed. 

462. Palatability. — In order to obtain the best results, 
the food should be relished by the animals. Palatability 
exerts a favorable influence upon digestibility and also 
upon the returns in animal products. Overripe and 
fibrous fodders generally lack palatability, because in the 
later stages of growth there is a smaller amount of the 
essential oils and other products that impart palatability. 
Mechanical condition and palatability of coarse fodders 
are closely associated, and the highest degree of digesti- 
bility of grains and fodders usually accompanies the best 
mechanical condition. 

463. Individuality. — When a number of animals are 
fed the same ration, individual differences are observed. 
Some animals are capable of digesting all foods more 
completely than are others, and some can digest one food 
more completely than another food. This is due to indi- 
viduality in digestive power and is particularly noticeable 
in experiments with sheep, where it has been found that 
all do not digest the different foods equally well. Also, 



DIGESTION AND NUTRITION 323 

digestion coefficients obtained in experiments with one 
kind of animal, as sheep, are not always applicable to 
other animals. Experiments with swine show that fiber 
is not so completely digested as with sheep or cows. 

464. Miscellaneous Factors Influencing Digestibility. 
— Experiments in cooking foods for animals show that 
cooked foods are no more completely digested by farm 
animals than uncooked foods. Cooking, however, is 
sometimes desirable in order to encourage animals to 
consume a larger amount of food. The wetting of food, 
causing fermentation, has been found to be slightly bene- 
ficial. However, if wetting is practiced, great care should 
be exercised to prevent excessive fermentation or the action 
of undesirable ferments. Drying and curing of fodders 
do not appear to exert any unfavorable influence upon 
digestibility, provided leaching and excessive bleaching 
are avoided. Green fodders, as a rule, appear to be 
slightly more digestible than cured fodders. In some 
cases, the laxative nature of a food prevents complete 
absorption of the nutrients before the material is expelled 
from the body. 

465. Application of Digestion Coefficients. — Too close 
application of digestion coefficients should not be made, 
but general comparisons where the experiments have 
been performed under similar conditions are allowable 
and give valuable results. The methods used for the 
determination of digestion coefficients have not been 
perfected, and a number of sources of minor error are 
introduced. In the case of the feces, the ether extract 
contains bile nitrogen, cleavage products, and a number of 
other non-fatty compounds. Hence the figures for the 
digestibility of the ether extract are invariably too low. 
Not all of the nitrogen of the feces is in indigestible form, 



324 AGRICULTURAL CHEMISTRY 

thus there is a tendency for the digestibility of the crude 
protein to be too low. Then, too, it is difficult to assign 
an absolute nitrogen factor for the determination of the 
crude protein. Notwithstanding these known imper- 
fections in determining the digestibility of foods, the 
general results are of great value to the farmer, as they 
indicate ways by which the largest returns, due to the 
highest degree of digestibility, can be secured. Some 
of the digestion coefficients of the more common food 
materials are given in the following table, which is taken 
from Bulletin No. 77, U. S. Department of Agriculture, 
Office of Experiment Stations : 

Digestion Coefficients. 



&3 

q e 

Green Fodders. 

Timothy 63.5 

Dent corn 67.8 

Oats 59.5 

Red clover 66.1 

Silage. 

Dent corn silage 65.1 

Flint " " 73.1 

Dent " " (im- 
mature) 65.6 67.4 34.3 51.3 70.6 67.4 80.2 

Cured Fodders. 

Timothy (average) ... 56.6 

" before bloom 60.7 

" past bloom . 53.4 

Dent corn fodder. ... 64.3 

Flint " " 68.6 

Dent and flint (imma- 
ture) 63.9 

Dent and flint (ma- 
ture) 68.2 



OS 


< 


ft) .9 

-a « 
v a 


u 

Via 


O <u 

MH ftj 


4) a 


65.6 


32.2 


48.1 


55-6 


65-7 


53-i 


69.8 


35-6 


59-7 


60.2 


73-7 


74.1 


60.9 


53-4 


71.8 


52.8 


62.6 


69.2 


68.1 


55-o 


67.0 


52.6 


77.6 


64-5 


67.1 


32.2 


48.3 


66.7 


68.6 


80.0 


76.1 


32.9 


62.8 


75-i 


76.9 


81.8 



57-9 


32.8 


46.9 


52.5 


62.3 


52.2 


61.5 


44.2 


56.8 


58.8 


64-3 


58.4 


54-5 


30.3 


45-i 


47.1 


60.4 


5i-9 


66.1 


3°-7 


50-4 


62.2 


68.0 


73-6 


71.7 


42.6 


60.0 


74-9 


70.3 


71.4 


65-7 


37-2 


5i-7 


66.0 


66.2 


72.2 


70.7 


30.6 


56.7 


65-8 


72.2 


73-9 



DIGESTION AND NUTRITION 



325 



Cured Fodders (cont.). 

Corn stover 

Red clover 

Grains and Seeds. 

Corn meal 

Gluten feed 

" meal 

Malt sprouts 

Wheat bran 

Oil-bearing Seeds. 

Cottonseed meal 

Linseed meal (old 
process) 

Roots. 

Mangels 

Potatoes (raw) 



OS 

57-2 
57-4 

89.4 
86.3 

89.7 
67.1 
62.3 

73-7 
78.7 

78.5 
75-7 









5 ~ 






c 




M X 




■d 

3 


<L> 


3 <L> 


a « 


O 


a 


w«3 


fc.2 


W 



59.1 32.6 35.9 64.2 57.9 70.4 
59.7 29.1 58.0 54.2 64.4 55.2 



89.6 

87-3 
90.4 
67.2 
65-7 



76.1 23.7 88.4 55.5 60.6 93.3 

81.2 ... 88.8 57.0 77.6 88.6 



67.9 


... 94.7 


92.1 


85.6 


78.0 89.2 


84.4 


88.2 


. . . 89.8 


94.4 


80.2 


32.9 68.1 




77-8 


28.6 69.4 


68.0 



84.8 16.4 74.7 42.8 91.3 

77.0 . . . 44.7 . . . 90.4 



13.0 



Some of the facts noticeable in the table are as follows : 
The highest degree of digestibility of a nutriment is 
usually obtained with foods which contain the largest 
amount of that nutrient. For example, clover hay con- 
tains more crude protein than timothy hay, and in 
general the protein of clover is more completely di- 
gested than that of timothy. In potatoes, there is a large 
amount of nitrogen-free extract compounds (starch), 
and in the table it will be observed that they are 
more completely digested than the crude protein which 
is present in smaller amount. Whenever a food contains 
nutrients in small amounts they are in dilute forms, and 
are not so completely extracted as when present in larger 
amounts. The coarse fodders are not so completely 
digested as the grains and milled products. In the coarse 
fodders, the digestion coefficients range from 30 to 65, 



326 AGRICULTURAL CHEMISTRY 

while in grains and milled products, the range in diges- 
tibility is from 70 to 95. 

466. Digestible Nutrients of Foods. — When the total 
nutrients in a food are multiplied by the digestion coeffi- 
cients, the available nutrients are secured. For example, 
clover hay contains 12 per cent crude protein, which is 
60 per cent digestible. The available or digestible crude 
protein of the clover hay is 7.2 (12 X 0.6 = 7.2). In 
like manner, all the digestible nutrients of foods are ascer- 
tained. The per cent of each nutrient is multiplied by 
its digestion coefficient, which gives the total available 
or digestible nutrients. When the average composition 
of American feeding stuffs and the average digestion 
coefficients are used, the average digestible or available 
nutrients are obtained. Such a table is given at the end 
of the chapter. In using this table, it should be remem- 
bered that the figures are those of average conditions, 
and may not be applicable to all cases, and while the 
amounts of nutrients given are fairly constant, they 
nevertheless vary. It is possible by giving due care to 
the production of crops to secure those containing the 
maximum nutrients, and then to feed the crops so as to 
secure the highest degree of digestibility and thus more 
nutrients than are given in the tables at the close of the 
chapter. For example, timothy hay may contain from 
5 to 9 per cent protein. That which contains 5 per cent 
is less completely digested than that containing 9 per cent. 
From the timothy with the highest degree of digestibility, 
there is about 7 per cent of the protein digestible and 
available, while from that with 5 per cent of crude protein 
there is from 2.5 to 3 per cent available. The avail- 
ability of the other nutrients also is in favor of the timothy 
hay with the larger amount of protein. In the feeding 



DIGESTION AND NUTRITION 



327 



of farm animals, particular attention should be given to 
the production of foods which contain the largest amounts 
of the most valuable nutrients and to combining and 
using them so as to secure the highest degree of digesti- 
bility. Digestion experiments have pointed out ways in 
which these results may be accomplished, and the experi- 
ments are valuable in indicating how the largest returns 
can be secured from the fodders and grains raised and 
fed upon the farm. 

Experiment 77. — Digestible nutrients of foods. Take the di- 
mensions of one of the measures given out for the experiment and 
calculate its capacity in quarts, dry measure (1 quart = 67.2 cubic 
inches). Weigh the measure, fill it with oats and weigh again. 
From the tables, calculate the pounds of digestible fat, protein, and 
carbohydrates in one quart of each of the foodstuffs. Tabulate 
the results as follows : 

Digestible Nutrients in Foods. 



Name of Food. 


Net Weight of 
Measure. 


Digestible Pounds per Quart. 




Grams. 


Pounds. 


Fat. 


Protein. 


C'bhydr'ts. 


Oats 

Bran 

Corn 

Oil meal 

Flour 

Shorts 













CHAPTER XXXVI 
Rational Feeding of Animals 

467. Balanced Rations. — A balanced ration is one 
which contains sufficient nutrients from a variety of foods 
to meet the requirements of the animal. Since the 
different classes of nutrients serve different purposes in 
the body, it is the object of rational feeding to combine 
foods so as to supply the nutrients in the right proportion 
for growth and work or for the production of milk, meat, 
or wool. Rational feeding is based upon (1) the food 
requirements of animals, and (2) the amount of digestible 
nutrients in foods. The food requirements of animals 
are determined by experiments. 

468. A Maintenance Ration is one which furnishes all 
of the nutrients required for maintaining the weight of 
the body and for performing all its functions without 
allowing any nutrients for growth, work, or other purposes. 
A maintenance ration simply sustains the animal, and 
makes no allowance for growth or work. When an 
animal is fed a maintenance ration, it neither gains nor 
loses in weight ; an equilibrium is established between 
the income and outgo of the food. The nitrogen in 
the proteids of the food consumed is all returned in the 
various waste products of the body. Since nitrogen is 
the characteristic element of protein, it is taken as the 
index for determining the maintenance requirements of 
animals. When the nitrogen in the waste products 
equals that in the food consumed, and no work has been 

328 



RATIONAL FEEDING OF ANIMALS 329 

performed, a maintenance ration has been fed, as the 
body has neither gained nor lost protein. Growth, 
work, and animal products are all produced from the 
excess of nutrients over those required for maintenance 
purposes. For example, a pig weighing 200 pounds 
requires about five pounds of grain per day for mainte- 
nance. If 5.5 pounds per day are fed, an increase in 
weight is secured only from the half pound in excess of 
the maintenence ration. 

469. Standard Rations. — For feeding purposes stand- 
ard rations have been proposed, giving the amounts of 
nutrients required by different classes of animals for 
different purposes. These tables have been prepared 
largely as the result of digestion experiments and feeding 
trials. The table in most common use is that prepared 
by Woulff and modified from time to time by various 
investigators. This table is given at the close of the 
chapter. 

470. Food Requirements of Animals. — In the feeding 
of balanced rations, tables of feeding standards should be 
used largely as guides. It is not necessary that the rations 
should, in all particulars, absolutely conform to the 
standards given. On the other hand, it is not advisable 
to have the amounts of nutrients in the rations vary 
in any large degree from the standards. It is difficult to 
specify the amounts of nutrients which, under all condi- 
tions, will meet the food requirements of all classes of 
animals. In previous chapters, it has been shown that 
the composition of forage crops is subject to variation, 
as is also their digestibility. Hence, tables giving the 
amounts of digestible nutrients are only approximately 
correct, and if assumed for all fodders and conditions, the 
calculated amounts of nutrients would, in some cases, 



330 AGRICULTURAL CHEMISTRY 

exceed, and in others fall short of, the standards given. 
On this account, it is not well to adhere too closely to 
fixed rules in the rational feeding of farm animals. When 
foods containing the largest amounts of nutrients are 
produced and so fed as to secure the highest degree of 
digestibility, smaller amounts are required than when foods 
low in available nutrients are used and injudiciously fed. 

471. Food Supply at Different Stages of Growth. — 
The amount and nature of the food consumed should vary 
with the period of growth. Rations for young and grow- 
ing animals should contain more protein and less of the 
non-nitrogenous compounds than rations for mature 
animals. This is because more food is required for 
building purposes in the early stages of growth than in 
later stages, when more is required for heat and energy. 
These facts may be observed from the table of feeding 
standards. For example, a calf three months old that 
weighs 150 pounds requires per day 0.6 pound digestible 
protein and 2.4 pounds digestible non-nitrogenous com- 
pounds. When the animal is a year old and weighs 500 
pounds, it requires 1.3 pounds of digestible protein and 
6.9 pounds of digestible non-nitrogenous compounds. 
The animal has increased in weight more than three times, 
while the additional demand for digestible protein has 
only doubled, but for the non-nitrogenous compounds it 
is four and one half times as great. 

When an excess of starchy and non-nitrogenous foods 
is fed to a young and growing animal, there is a tendency 
toward the production of a poor muscular and bony 
framework and premature fattening. To produce 
balanced growth in young animals, careful attention 
should be given to the amount and nature of the nutrients 
supplied in the food. 



RATIONAL FEEDING OF ANIMALS 33 1 

472. Food Requirements of Horses. — In feeding work 
horses, the object is to provide available nutrients for the 
production of energy, because it is the energy from the 
food which enables the horse to do his work. Experi- 
ments show that for maintenance purposes, a iooo-pound 
horse requires about 17.5 pounds of hay per day contain- 
ing a half pound of digestible protein and 7 to 7.5 pounds 
of digestible non-nitrogenous compounds. Such a ration 
does not provide any nutrients for work. In the table 
at the close of the chapter are given the amounts of 
nutrients required for average work. Any increase in 
work should be followed by a corresponding increase of 
food. Average work is best accomplished with a ration 
containing 22 to 24 pounds of dry matter per day, of 
which about 1.8 pounds are digestible protein and 11 to 
1 1.5 pounds are digestible nitrogen-free extract. It is 
estimated that about one third of the energy derived 
from the food is utilized as energy in the performance 
of work. The best results are obtained when an even 
draft is made upon an animal, as experiments show that 
less energy is required for average work continuously 
than for severe work for a short time followed by rest. 

473. Selection of Food for Horses. — For light work, 5 
to 7 pounds per day of mixed grains are usually sufficient 
if combined with 12 to 15 pounds of coarse fodder, as 
timothy hay. For average work more food is required, 
and the amount of grain should be about equal in weight 
to the coarse fodder. For heaviest work, the grain should 
exceed the fodder in weight. Pure clover hay, on account 
of its mechanical condition, is not suitable for the feeding 
of horses. Timothy hay, blue grass, and the different 
varieties of prairie hay are all good if cut and cured when 
medium ripe. Early cut fodders are not so satisfactory 



332 AGRICULTURAL CHEMISTRY 

for horses as for other kinds of animals. There is a 
tendency to confine the ration of horses too largely to 
one grain, oats, which usually makes an expensive ration. 
Experiments show that a larger variety of foods is 
desirable. Corn, barley, ground wheat, bran, and other 
milled products may form a part of the ration for work 
horses. For purposes of variety, carrots or potatoes in 
small amounts may be fed. Oil meal also to the extent of 
about one fourth pound per day is valuable. For average 
work, grinding of grains is not necessary ; for hard work, 
coarse grinding results in availability of a larger amount 
of the net energy of the foods. 

474. Foods required for Beef Production. — According 
to the table of feeding standards from 25 to 30 pounds 
dry matter containing 2.5 to 3 pounds digestible protein, 
and about 15 pounds digestible carbohydrates are re- 
quired for a 1000-pound animal. As pointed out by 
Jordan, in " Feeding of Farm Animals," these standards 
are too high for economic feeding. As the result of 
feeding trials, 15 pounds digestible organic matter per 
day for a 1000-pound animal have been found sufficient. 
A ration containing 15 pounds digestible dry matter, 
about 1.80 pounds digestible protein, 13 pounds digestible 
nitrogen-free extract compounds, and 0.7 pound digestible 
ether extract was found satisfactory. When too little 
protein is supplied in a ration, the meat is of poorer 
quality than when more is available, so as to produce a 
normal amount of circulatory proteids in the system. In 
beef production, the aim should be to supply sufficient 
available protein for maintenance purposes, and a small 
amount for the other needs of the body, the fat being 
produced from the less expensive nutrients, as carbohy- 
drates and ether extract. When the fat is produced 



RATIONAL FEEDING OF ANIMALS 333 

from an excess of protein in the food, the cost of produc- 
tion is unnecessarily large. The protein supply in beef 
production should vary with the stage of fattening. 
Experiments at the Pennsylvania Station show that 0.42 
pound digestible protein, 6.77 pounds digestible non- 
nitrogenous compounds, and 0.13 pound digestible ether 
extract are required for maintenance purposes. At 
different stages of growth, different amounts of food are 
required to produce a pound of gain. This fact is particu- 
larly noticeable in experiments at the Kansas Station 
from which the following data are taken : 

Grain required for 
1 pound gain. 

After 56 days 7.30 

After 84 days 8.07 

After 122 days 8.40 

After 140 days 9.01 

After 168 days 9.27 

After 182 days 10.00 

In the production of beef, palatability of the ration is 
an important factor ; this is best secured by combining a 
number of grains and coarse fodders. 

475. Selection of Foods for Beef Production. — Foods 
which are valuable for milk production are likewise 
valuable for beef production ; bran, oil meal, cottonseed 
meal, corn, barley, shorts, middlings, and screenings are 
among the best grain and milled products. Pasture 
grass, clover hay, alfalfa, corn silage, corn fodder and 
mixed hays are all valuable coarse fodders. Roots and 
tubers, to the extent of 10 to 15 pounds per day, may 
also be added to a beef ration. The amount of grain 
should range from 10 to 18 pounds per day, with from 12 
to 18 pounds of coarse fodder. Occasionally heavy grain 



334 AGRICULTURAL CHEMISTRY 

feeding is resorted to in the fattening of steers. When 
grains and milled products are cheap, this practice is 
often economical, as it converts a cheap grain into a more 
valuable marketable product. Ordinarily the cost of 
production is greater with a heavy grain ration than with 
a light or medium one, and when more than 12 pounds of 
grain per day are fed, the additional amount is fed at a loss. 
When grains and feeding stuffs are high in price, heavy 
grain feeding is not economical. It should be the aim, 
in the production of beef, to secure the larger portion of 
growth, as well as the larger portion of the increase during 
the fattening, from high-grade coarse fodders, and supple- 
ment them with medium amounts of grain and milled 
products. The amount of grain that can be fed econom- 
ically is regulated by its cost and the market price of the 
beef product. 

476. Food Requirements of Dairy Cows. — For the 
production of milk, a more liberal supply of digestible 
protein is required than for beef production. From 0.4 
to 0.5 pound of digestible protein and from 7 to 7.5 
pounds of digestible carbohydrates are required for main- 
tenance. A ration should contain, in addition, 1.2 to 1.8 
pounds digestible protein and 4 to 6 pounds digestible 
carbohydrates, because milk cannot be produced econom- 
ically on too scant an amount of nutrients. According 
to the standard feeding tables, a ration for a cow giving 
a heavy yield of milk should contain 3 2 pounds dry matter, 
3.3 pounds digestible protein, and 13 pounds carbohy- 
drates. This is a larger amount of protein than is neces- 
sary for economical milk production. Under average 
conditions, a ration containing about 27 pounds dry 
matter, 1.8 to 2 pounds digestible protein, and 11 to 13 
pounds digestible carbohydrates will prove more economi- 



RATIONAL FEEDING OF ANIMALS 335 

cal than one containing larger amounts of protein. In a 
milk ration, proteids must be furnished for the produc- 
tion of the albumin and casein in the milk. In 1 5 pounds 
of milk there is about one half pound of proteids, as 
albumin and casein, and this must be supplied from the 
food. About as much more protein is necessary to supply 
the energy to produce the milk as is required for main- 
tenance and the milk proteids. In an ordinary dairy 
ration, practically one fourth of the proteids is recovered 
in the milk as casein and albumin, one fourth is indi- 
gestible, while one half is present in the liquid waste and 
represents the protein required for maintenance and the 
production of milk. The nutrients in a dairy ration 
should vary with the milk yield, as given in the table of 
feeding standards, but it is not necessary to adhere too 
closely to the figures. 

In calculating a dairy ration, it will be found that 
when ordinary foods are combined, the amount of ether 
extract or crude fat will exceed the figures given in the 
table. Provided the ration contains the requisite diges- 
tible protein, and does not yield more than 32,000 calories, 
there is no objection to the crude fat amounting to 0.6 
pound per day. It ought not, however, in an average 
ration, exceed 0.8 pound. 

477. Selection of Foods for Dairy Cows. — The amount 
of grain which a dairy cow should receive varies from 7 
to 12 pounds per day. Occasionally 15 pounds can be 
fed economically, but, as a rule, medium grain rations of 
from 7 to 1 2 pounds produce milk and butter more econom- 
ically than either light or heavy rations. As in beef 
feeding, when more than 12 pounds per day of grain are 
fed, the additional amount is not used economically, and 
is generally a loss. The coarse fodder in a dairy ration 



336 AGRICULTURAL CHEMISTRY 

may vary from 18 to 50 pounds per day, according to the 
amount of water in the foods. The ration should contain 
from 25 to 30 pounds of dry matter. When silage is 
fed, 20 to 40 pounds may be used because of its high 
water content. In feeding roots, from 15 to 20 pounds 
per day will be found economical. It is not desirable 
to restrict dairy cows to a ration of one grain or milled 
product. Better results are secured from a mixture of 
two or three grains. No great differences have been 
observed in the milk-producing value of the different 
grains and milled products. A pound of one grain in a 
mixed ration will produce about as good results as a 
pound of another grain. For example, wheat has been 
found to have practically the same feeding value as corn, 
oats, or barley. Common farm grains will give about 
the same yield of milk and butter-fats as average mill 
feeds like bran or shorts. Mixed wheat feed consisting 
of bran, shorts, or middlings and red-dog or feeding flour 
is a valuable dairy feed. Oil meal in medium amounts 
in a ration produces from 20 to 25 per cent better re- 
sults than bran. Oil meal, cottonseed meal, and gluten 
meal all have about the same milk-producing value. 

Clover hay, corn silage, corn fodder, alfalfa, and oat 
hay are among the most valuable coarse fodders for milk 
production, preference being usually given to clover hay 
when cut in early or full bloom. When silage is' not 
fed, roots should always form a part of a dairy ration. 
Roots are valuable largely because of their palatability 
and the favorable influence which they exert upon diges- 
tion, rather than for any large amount of nutrients. 

478. Food Requirements of Swine. — The nutrients 
required by swine vary with the stage of growth more than 
in the case of other animals. In the earlier stages of 



RATIONAL FEEDING OF ANIMALS 337 

growth, particular attention should be given to furnishing 
a liberal supply of available protein and mineral matter. 
A ration for a ioo-pound animal should contain about 
0.5 pound digestible protein and 2.5 pounds digestible 
carbohydrates, while that for a 200-pound animal should 
contain about 0.6 pound digestible protein and nearly 
4 pounds digestible carbohydrates. For growing pigs, 
a mixture of shorts and corn or shorts and barley with 
skim milk will be found preferable to any single grain. 
Skim milk should not be used in greater amounts than 
3 pounds for each pound of grain. Five pounds of skim 
milk will produce as much gain in weight as one pound 
of grain. For fattening pigs the grain mixture should 
contain more corn than shorts. Coarsely ground barley is a 
valuable food and produces a good quality of pork. Peas 
may form about one third of the grain mixture. For 
fattening purposes, foods with a large amount of digestible 
protein are not as essential as for growing animals because 
the excess of protein is used for the production of fat, 
which can be produced from less expensive nutrients, as 
carbohydrates. The food should not be too concentrated in 
character. Many of the grains are so highly digestible 
that they leave in the digestive tract only a little insoluble 
matter to dilute the waste products. This is particularly 
true of peas and corn. Charcoal and a small amount 
of corn and cob meal are found useful to correct such 
deficiencies. Also some forage crop, as chopped, steamed, 
or soaked clover, should be at the disposal of the animal. 
Wheat, barley, and rye, if fed, should be coarsely ground, 
but with corn, grinding is not so essential. Bone meal, 
dried blood, and meat scrap are valuable m a ration for 
pigs, particularly if corn is the principal grain used. 
Among the forage crops, rape, clover, alfalfa, sorghum, 



338 AGRICULTURAL CHEMISTRY 

and corn will be found most valuable for pork produc- 
tion. 

479. Food Requirements of Sheep. — The standard 
for the rations of sheep, as given in the tables, can be 
adhered to more closely than the standards for any other 
class of farm animals. This is because a large number 
of feeding trials and experiments have been made with 
sheep. They require more nutrients than do beef animals, 
and they are capable of making equally good returns 
from the food consumed. Experiments by Lawes and 
Gilbert show that during the process of fattening only a 
slight increase in nitrogen takes place ; the gain in weight 
is largely an increase in fat. During the growing period, 
a more liberal allowance of available protein is required 
than for fattening. Farm foods need but little reinforce- 
ment with mill and other products for the production of 
mutton. Henry, in " Feeds and Feeding," states that 
about 500 pounds of corn and 400 pounds of clover will 
produce 100 pounds of gain in live weight of lambs, and 
he gives these figures for calculating the cost of production. 
The grinding of grains is not so necessary in sheep feeding 
as in dairy feeding. Among the grains, corn, barley, 
wheat, and oats have all been found valuable. Wheat 
screenings are extensively utilized in the production of 
mutton. Oil meal and other mill by-products also are 
suitable, provided their cost is not too high. Among 
the coarse fodders, clover hay, alfalfa, corn fodder, and 
silage are particularly valuable. Roots should form a 
part of the ration. Variety and palatability should be 
considered. 

480. Calculation of Balanced Rations. — In calculating 
a balanced ration, first the food requirements of the ani- 
mal, as given in the table of feeding standards, are noted. 



RATIONAL FEEDING OF ANIMALS 339 

Then a reasonable variety of coarse fodders, grains, and 
roots is selected on the basis of cost, as explained in Sec. 
483, and a trial ration is calculated, using the approxi- 
mate amounts of foods as given in the various sections 
relating to the food requirements of animals. The 
amounts of digestible nutrients in the foods selected are 
calculated and the totals of the different nutrients deter- 
mined. If these correspond with the figures given in 
the table, a reasonably well-balanced ration is secured. 
In case the nutrients are present in the right proportion 
but deficient in amounts, the weights of foods used are 
increased ; if excessive, they are reduced. Should the 
ration be deficient in digestible protein, a small amount 
of some food containing a liberal supply of this nutrient 
may be added. Finally, when the requirement as to 
nutrients is satisfied, the various other factors, as bulk, 
suitable combinations, cost, and labor involved in prepa- 
ration are to be considered. 

Example. — Calculate a ration for a dairy cow giving a large 
milk yield. The standard ration calls for 1.8 to 2 pounds digestible 
protein and from 10 to 12.5 pounds digestible carbohydrates. It is 
necessary to combine the coarse fodders and grains so as to secure 
approximately these amounts of nutrients. A trial ration is cal- 
culated, composed of 10 pounds each of clover hay and corn fodder, 
20 pounds of mangels, 5 of bran, and 3 of oats. The digestible nu- 
trients in these materials, as given at the close of the chapter, are 
as follows : 

Digestible Nutrients. 



Protein. 

Wheat 12.9 

Mangel beets 1.1 

Clover hay 6.8 

Corn fodder 2.5 

Oats 9.2 



Fat. 


Carbohy- 
drates, etc. 


3-4 


40.I 


O.I 


5-4 


i-7 


35-8 


1.2 


34.8 


4.2 


47-3 



340 AGRICULTURAL CHEMISTRY 

These figures are on the basis of ioo pounds. The 
amounts of nutrients in one pound are found by moving 
the decimal point two places to the left. Multiplying 
the pounds of food by the per cent of digestible nutri- 
ents, the pounds of digestible nutrients will be found to 
be as follows : 

Pounds of Digestible Nutrients. 

Carbohy- 
Pounds. Protein. Fat. drates, etc. 

10 Clover hay 0.68 0.17 3.58 

10 Corn fodder 0.25 0.12 3.48 

20 Mangel-wurzels 0.22 0.02 1.08 

5 Bran 0.64 0.16 2.00 

3 Oats 0.28 0.13 1.42 

2.07 0.60 n.56 

Compared with the standard ration, it will be observed 
that the amounts of nutrients are approximately as given 
in the table, suggesting that as far as total nutrients are 
concerned, the ration is a reasonable one. The coarse 
fodder, grain, and roots are about in the proportions 
given in Section 477. As to the effects of the various 
foods, the bran, mangels, and clover hay might possibly 
prove somewhat laxative in character, and while the 
ration supplies all of the requisites as to dry matter and 
amount of nutrients, it would be necessary to note the 
effect upon the animal, before concluding it satisfactory 
in all respects. 

481. Nutritive Ratio. — The nutritive ratio is the ratio 
which exists between the digestible protein and the 
digestible non -nitrogenous compounds. A nutritive ratio 
of 1 to 6.7 means that for every 1 pound of crude pro- 
tein there are 6.7 pounds of digestible non-nitrogenous 
compounds. A wide nutritive ratio means a large amount 
of non-nitrogenous to nitrogenous compounds, while 



RATIONAL FEEDING OF ANIMALS 34 1 

a narrow nutritive ratio means a small amount of non- 
nitrogenous to nitrogenous compounds. 

To calculate the nutritive ratio, first determine the 
pounds of digestible protein in the food, then the pounds 
of digestible carbohydrates, etc. Multiply the pounds 
of digestible ether extract by 2.2, because the fat produces 
2.2 times as much heat, consequently is considered 2.2 
times more concentrated than the nitrogen-free extract 
compounds. Add the digestible fiber, nitrogen-free ex- 
tract, and corrected ether extract and divide the sum by 
the digestible protein ; the result is the nutritive ratio. 
The nutritive ratio of the ration given is 6.23 (0.6 X 2.3 
= 1.32) (1.32 + 11.56 = 12.88) (12.88 -3- 2.07 = 6.23). 

482. Caloric Value of Rations. — The caloric value of 
a ration is determined by multiplying the pounds of 
digestible ether extract by the factor 4225 and adding this 
to the number secured by multiplying the sum of the 
digestible protein and carbohydrates by i860. As used 
in the calculation of rations, the carbohydrates include 
the nitrogen-free extract compounds and the digestible 
fiber. The term carbohydrates is used in the broad 
rather than the restricted sense. 

Problem 1. — Calculate a ration for a 1200-pound horse at light 
work. Use any foods desired. 

Problem 2. — Calculate a ration for a 1200-pound horse at heavy 
farm labor. 

Problem j. — Calculate a ration for a pig weighing 100 pounds. 

Problem 4. — Calculate a ration for a pig weighing 250 pounds. 

Problem 5. — Calculate a ration for a dairy cow giving a full flow 
of milk. 

Problem 6. — Calculate a dairy ration for average milk yield. 

Problem 7. — Calculate a ration for a sheep weighing 100 pounds. 

Problem 8. — Calculate a ration for a growing steer weighing 500 
pounds. 

Problem 9. — Calculate a ration for a 1 200-pound steer, fattening 
period. 



342 AGRICULTURAL CHEMISTRY 

483. Comparative Cost and Value of Grains. — The 

market value of grains frequently differs from their actual 
food value. That is, a given sum of money if invested 
in one food article will often procure a larger amount of 
digestible protein and other nutrients than if invested in 
other foods. To illustrate : If corn is 50 cents and oats 
30 cents per bushel, $1 will purchase either 112 pounds 
of corn or 107 pounds of oats. Which is the cheaper and 
more valuable for feeding purposes? The digestible 
nutrients in 100 pounds of corn and oats are as follows : 



Corn 
Oats. 



Digestible nutrients. 
Protein. Fat. 


Pounds per hundred 
Carbohydrates, etc. 


7-9 4-3 


66.7 


9.2 4.2 


47-3 



Protein. 


Fat. 


Carbohy- 
drates. 


Calories. 


8.85 


4.82 


74-7 


175,684 


9.84 


4-5° 


SO.6 


13^407 



The amounts of digestible nutrients in 112 pounds of 
corn and 107 pounds of oats obtained by multiplying by 
the per cent of digestible nutrients are : 

Pounds. 

Corn 112 

Oats 107 

There is a difference of about 1 pound of digestible 
protein in favor of the oats and 24 pounds of digestible 
carbohydrates in favor of the corn ; the dollar's worth of 
corn would also contain about 44,000 more calories. At 
the prices given, corn rather than oats should form the 
larger portion of a grain ration for work horses, beef and 
dairy animals, and swine and sheep. For growing animals, 
however, a large amount of corn is not desirable. 

In deciding the comparative value of foods on the basis 
of their nutrient content, preference should usually be 
given to the protein, but when the difference in digestible 
protein is small, the preference should be given to the 
food containing the largest amount of available carbo- 



RATIONAL FEEDING OF ANIMALS 



343 



hydrates and number of calories. Comparisons between 
foods which are very unlike in character of nutrients cannot 
safely be made. It is not possible to assign an absolute 
value to any food upon the basis of any one or all of its 
digestible nutrients, because the comparative value of the 
different nutrients has not, as yet, been definitely ascer- 
tained. In the selection of foods, it will frequently be 
found that a given sum of money can be invested in the 
purchase of two foods, one nitrogenous and the other non- 
nitrogenous, better than in the purchase of one. The re- 
sults of actual feeding tests should also be considered 
before definitely selecting foods. When both the available 
nutrients and the results of feeding experiments are 
considered, an accurate idea of the comparative cost and 
value of grains and milled products can be formed. 

Problem. — Complete the following table and calculate the avail- 
able nutrients and calories that can be procured for $i when the 
various foods are at different prices. In making the calculations, 
use the prices of your local or home market. Select three of the 
cheapest and three of the most expensive foods from the list. 





Price 

per 

Bushel 

or Ton. 


Pounds 
for $i.oo. 


Nutrients procurable for $i.oo. 
Pounds Digestible Nutrients. 




Protein. 


Carbohy- 
drates. 


Ether 
extract. 


Calories. 


Corn 

Oats 

Wheat feed .... 
Wheat bran . . . 
Wheat shorts . . 

Oil meal 

Linseed meal . . . 
Cottonseed meal 
Gluten meal. . . 















344 AGRICULTURAL CHEMISTRY 

484. Sanitary Conditions. — Satisfactory results in the 
feeding of animals can be secured only under the best 
sanitary conditions. When animals are kept in crowded 
quarters, deprived of pure air and sunlight, they fail to 
make the best use of the food consumed. Carbon dioxid 
thrown off from the lungs and ammonia produced from 
decaying manure form ammonium carbonate, a volatile 
and irritating compound. Sunlight is an important factor 
for promoting animal growth. Experiments with grow- 
ing calves show that under the same conditions of food 
and management, animals reared with an abundance of 
sunlight make better gains in weight, and are more 
vigorous than those confined in dark quarters. The best 
results are obtained in the feeding of animals when their sur- 
roundings are most sanitary. A large amount of available 
energy is often lost in warming up cold, wet bedding. Pure 
water, pure air, sunlight, clean quarters, and dry bedding 
are as necessary to animals as is a well-balanced ration. 

Table of Feeding Standards. 

Per 1000 lbs. live weight, daily. 



Digestible organic substances. 



Dry 
sub- 
Kind of animals. stance, 
lbs. 

Fattening bo vines 30 

Milk cows : 

Daily milk yield, 11 lbs. . . 25 

Daily milk yield, i6| lbs. . . 27 

Daily milk yield, 22 lbs.. . . 29 

Daily milk yield, 27! lbs. . . 32 

Sheep 22 

Fattening sheep, first period 30 

Horses : 

Light work 20 

Moderate work 24 

Severe work 26 





Car- 








Pro- 


bohy- 






Nutri- 


tein. 


drates. 


Fat. 


Total. 


tive 


lbs. 


lbs. 


lbs. 


lbs. 


ratio 1 


2-5 


15- 


o.5 


18.O 


6-5 


1.6 


10. 


°-3 


II.Q 


6.7 


2.0 


11.0 


0.4 


13-4 


6.0 


2-5 


13.0 


0.5 


16.0 


5-7 


3-3 


13.0 


0.8 


17. 1 


4-5 


i-3 


11. 


°-3 


13-5 




3-° 


15.0 


0.5 


18.5 


5-4 


i-5 


9-5 


0.4 


11. 4 


7.0 


2.0 


11. 


0.6 


13.6 


6.2 


2-5 


13-3 


0.8 


16.6 


6.0 



RATIONAL FEEDING OF ANIMALS 



345 



Per iooo lbs. live weight, daily. 
Digestible organic substances. 



Dry 
sub- 
Kind of animals. stance, 
lbs. 
Fattening swine : 

First period 36 

Second period 32 

Third period 25 

Growing cattle (dairy breeds) : 



Age in 
months. 

2" 3 

3" 6 

6-12 

12-18 

18-24 

Beef breeds : 

2- 3 

3" 6 

6-12 

12-18 

18-24 

Sheep : 

4- 6 
8-1 1 

Swine : 

2- 3 

3- 5 

5- 6 



Live weight 
per head, lbs. 

I50 

300 

500 

700 

900 



65 
IOO 

45 
no 

150 



23 
24 
27 
26 
26 

23 
24 

25 
24 
24 

26 
24 

44 
35 
33 



Pro- 
tein, 
lbs. 


Car- 
bohy- 
drates. 
lbs. 


Fat. 
lbs. 


Total, 
lbs. 


Nutri- 
tive 
ratio 1: 


4-5 


25. 


0.7 


30.2 


5-9 


4.0 


24. 


0.5 


28.5 


6-3 


2.7 


18. 


0.4 


21. 1 


7.0 



4.0 

3-o 
2.0 
1.8 
i-5 

4.2 

3-5 
2.5 
2.0 
1.8 

4.4 
3-° 

7.6 
5-o 
4-3 



13.0 
12.8 
12.5 
12.5 
12.0 

13.0 
12.8 
13.2 
12.5 
12.0 

15-5 
14-3 

28.0 
23.1 
22.3 



2.0 
1.0 

0.5 
0.4 

o-3 



0.9 

0.5 

1.0 
0.8 
0.6 



21.0 
16.8 
15.0 
14.7 
13.8 

19.2 
17.8 
16.4 
15.0 
14.2 

20.8 
17.8 

35-7 
28.9 
27.2 



4-5 
5-i 
6.8 

7-5 
8-5 

4.2 

4.7 
6.0 
6.8 
7.2 

4.0 

5-2 

4.0 

5.0 
5-5 



Digestible Nutrients in Fodders 

Digestible nutrients in 100 lbs. 



Name of feed. 



Dry matter 
in 100 lbs. 



Corn (all analyses) 89.1 

Dent corn 89.4 

Flint corn 88.7 

Sweet corn 91.2 

Corn cob 89.3 

Corn and cob meal 84.9 



Protein. 
7-9 
7-8 
8.0 
8.8 
0.4 
4.4 



Carbohy- 
drates. 

66.7 

66.7 

66.2 

63.7 
52.5 
60.0 



Ethei 
extract. 

4-3 
4-3 
4-3 
7.0 

0.3 
2.9 



346 



AGRICULTURAL CHEMISTRY 



Digestible nutrients in ioo lbs. 



Name of feed. 

Corn bran 90 

Gluten meal 91 

Germ meal 89 

Hominy chops 88 

Wheat 89 

Wheat bran 88 

Wheat bran (spring wheat) . 88 

Wheat bran (winter wheat) . 87 

Wheat feed 88 

Wheat shorts 88 

Wheat middlings 87 

Wheat screenings 88 

Rye 88 

Rye bran 88 

Rye shorts 90 

Barley 89 

Malt sprouts 89 

Brewers' grains (wet) 24 

Brewers' grains (dried) 91 

Oats 89 

Oat feed or shorts 92 

Oat hulls 90 

Buckwheat 87 

Buckwheat bran 89 

Flaxseed 90 

Linseed meal (old process) . . 90 

Linseed meal (new process) . 89 

Cottonseed meal 91 

Coarse Fodders. 

Fodder corn (green) 20 

Fodder corn (field-cure J) ... 57 

Corn stover (field-cured) .... 59 

Fresh Grass. 

Pasture grasses (mixed) .... 20 

Kentucky blue grass 34 

Timothy, different stages. . . 38 

Oat fodder 37 

Peas and oats .... 16 



natter 




Carbohy- 


Ether 


jibs. 


Protein. 


drates. 


extract 


•9 


7.4 


59-8 


4.6 


.8 


25.8 


43-3 


II. O 


.6 


9.0 


61.2 


6.2 


•9 


7-5 


55-2 


6.8 


•5 


I0.2 


69.2 


1-7 


.1 


12.2 


39-2 


2.7 


•5 


12.9 


40.1 


3-4 


•7 


I2.3 


37-1 


2.6 


.0 


*3-3 


40.5 


4.0 


.2 


12.2 


50.0 


3-8 


•9 


12.8 


53-o 


3-4 


•4 


9.8 


51.0 


2.2 


•4 


9.9 


67.6 


1.1 


•4 


n-5 


50.3 


2.0 


•7 


11. 9 


45-1 


1.6 


.1 


8.7 


65.6 


1.6 


.8 


18.6 


37-i 


i-7 


•3 


3-9 


9-3 


1.4 


.8 


IS-7 


36.3 


5-i 


.0 


9.2 


47-3 


4.2 


•3 


12.5 


46.9 


2.8 


.6 


i-3 


40.1 


0.6 


•4 


7-7 


49.2 


1.8 


•5 


7-4 


30.4 


1.9 


.8 


20.6 


17.1 


29.0 


.8 


29-3 


32.7 


7.0 


•9 


28.2 


40.1 


2.8 


.8 


37-2 


16.9 


12.2 


•7 


1.0 


11. 6 


0.4 


.8 


2-5 


34-6 


1.2 


•5 


i-7 


32.4 


0.7 


.0 


2-5 


10.2 


o-5 


•9 


3-o 


19.8 


0.8 


•4 


1.2 


19.1 


0.6 


.8 


2.6 


18.9 


1.0 


.0 


1.8 


7-i 


0.2 



RATIONAL FEEDING OF ANIMALS 



347 



Digestible nutrients in ioo lbs. 



Dry matter 

Name of feed. in ioo lbs. 

Hay. 

Timothy 86.8 

Redtop 91.9 

Kentucky blue grass 78.8 

Hungarian grass 92.3 

Mixed grasses 87.1 

Rowen (mixed) 83.4 

Oat hay 91. 1 

Straw. 

Wheat 90.4 

Oat 90.8 

Fresh Legumes. 

Red clover, difL stages 29.2 

Alsike, bloom 25.2 

Crimson clover 19. 1 

Legume, Hay, and Straw. 

Red colver, medium 84.7 

Red clover, mammoth 78.8 

Alsike clover 90.3 

Alfalfa 91.6 

Cowpea 89.3 

Silage. 

Corn 20.9 

Roots and Tubers. 

Potato 2 1. 1 

Sugar-beet 13.5 

Mangel beet 9.1 

Rutabaga 11.4 

Carrot 11.4 

Miscellaneous. 

Pumpkin (field) 9.1 

Beet pulp 10.2 

Cow's milk 12.8 

Skim milk (gravity) 9.6 

Skim milk (centrifugal) 9.4 

Buttermilk 9.9 

Whey 6.6 





Carbohy- 


Ether. 


Protein. 


drates. 


extract, 


2.8 


43-4 


1.4 


4.8 


46.9 


1.0 


4.8 


37-3 


2.0 


4.5 


5i-7 


i-3 


5-9 


40.9 


1.2 


7-9 


40.1 


i-5 


4-3 


46.4 


1. 5 


0.4 


36.3 


0.4 


JH.2 


38.6 


0.8 


2.9 


14.8 


0.7 


2.7 


i3-i 


0.6 


2.4 


13-9 


0.5 


6.8 


35-8 


i-7 


5-7 


32.0 


1.9 


8.4 


42-5 


1. 5 


11. 


39-6 


1.2 


16.8 


38.6 


1.1 



0.9 



n-3 



0.7 



0.9 


16.3 


O.I 


I.I 


10.2 


O.I 


I.I 


5-4 


O.I 


1.0 


8.1 


0.2 


0.8 


7.8 


0.2 


1.0 


5-8 


°-3 


0.6 


7-3 




3.6 


4.9 


3-7 


3-i 


4-7 


0.8 


2.9 


5-2 


o-3 


3-9 


4.0 


1.1 


0.8 


4-7 


°-3 



CHAPTER XXXVII 
Composition of Animal Bodies 

485. Water and Dry Matter. — About half of the live 
weight of an animal is water. In fat animals, the pro- 
portion of water is less than in lean animals. The same 
general classes of organic compounds present in plants, 
as non-nitrogenous and nitrogenous, are found also in 
animal bodies ; the animal forms, however, are usually 
somewhat more complex than the plant forms. Animal 
bodies are characterized by containing a high per cent of 
fat and proteid materials and a low per cent of non- 
nitrogenous compounds other than fat. 

486. Mineral Matter. — The ash elements in the animal 
body are the same as those found in plants, and are 
nearly all furnished from vegetable sources. The body 
of an animal, live weight basis, contains from two to four 
per cent of mineral matter, from half to three fourths of 
which is present in the bones, while the remainder is 
in solution in the various fluids, as the blood, chyle, etc., 
and deposited and combined with the solid and fleshy 
tissues of the body. Silicon in animal bodies is found 
mainly in the hair, wool, and feathers. Sodium and 
chlorin, while unnecessary to plants, are absolutely 
necessary to animals. A thousand parts of blood yield 
about 4 parts of mineral matter, of which 1.2 are sodium 
chlorid. In the blood, salt is necessary as a solvent for 
the proteids. 

The per cent of ash in the carcasses of different animals 

348 



COMPOSITION OF ANIMAL BODIES 349 

varies, being greatest in the half -fat steer or ox and 
least in the fat pig. In the process of fattening, the 
percentage amount of ash is decreased. 

As in the case of the plant, the mineral matter of the 
animal body must be secured and assimilated in the 
early stages of growth. Young pigs, or other young 
animals, fed exclusively on food which, like corn, is poor in 
digestible mineral matter, have bones which are weak 
and do not furnish a framework strong enough for the 
perfect development of the body in its last stages of growth. 
The same elements which are essential for plant growth 
are also essential for animal growth. 

487. Fat. — The per cent of fat in the carcasses of 
animals ranges from 14 to 45 per cent of the live weight. 
The carcasses of fattened steers of good quality are about 
one third fat ; in moderately fat 
sheep there is somewhat more, 
while the largest amount is pres- 
ent in the body of the very fat 
pig, with the very fat sheep as a 
close competitor. "It is thus 
seen that animal food of reputed 
high quality as sold by the 

1 1 1 1-1 1 8eef::: I. ash 

butcher, and to which such a -*ound-« £.refuse 

highly nitrogenous character is Fig. 99. — Composition of meat. 

usually attributed, will consist of fat to the extent of 
one third to one half of its total weight." (Lawes and 
Gilbert.) 

488. Nitrogenous Matter is present to the extent of 
10 to 18 per cent in the live animal, being least in the very 
fat pig and most in the half -fat ox. The offal parts, as 
the head, feet, tail, hair, wool, and horns, are rich in 
nitrogen, but not so rich as the flesh. Beef -yielding 




35° AGRICULTURAL CHEMISTRY 

animals, on the whole, contain rather more nitrogenous 
compounds than sheep, which in turn contain more than 
pigs. A large amount of the nitrogenous compounds of 
sheep and lambs is found in the wool (50 to 55 per 
cent). About 75 per cent of the carcass of the sheep is 
consumed as food ; thus it will be seen that much less 
than half of the total nitrogen is really made use of as 
human food. Of the fattened pig, about three fourths of 
the nitrogenous compounds are in the edible carcass, 
from 6 to 7 parts are in the bone, and about one quarter 
is in the offal. About 8 per cent of the nitrogenous 
compounds of the offal and a little over three fourths of 
the total nitrogenous compounds of the pig are consumed 
as food. About two thirds of the entire nitrogen of the 
calf and steer are in the butcher's carcass, and about 
12 per cent in the bones. From 5 to 7 per cent of the 
nitrogen of the offal parts and about 60 per cent of the 
total nitrogen of the steer are utilized as human food. 

In the table of relative composition of animal bodies, 
it will be noticed that the mineral matter increases and 
decreases with the nitrogenous matter. In the carcasses 
of all animals, it will be observed that the fat always ex- 
ceeds the nitrogenous matter, except in the case of the 
lean calf. In the bodies of animals in good condition, there 
is usually twice as much fat as protein. The following 
table is from the extensive work of Lawes and Gilbert. 

489. Proteids of Meat. — Lean meat, fat-free, is a 
concentrated nitrogenous material composed mainly of 
proteids, but containing also small amounts of amides, 
albuminoids, and, in some cases, alkaloidal bodies. The 
proteids are mainly in insoluble forms ; a small amount, 
however, is soluble. The principal soluble meat proteids 
are albumin and syntonin. 



COMPOSITION OF ANIMAL BODIES 



351 



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352 AGRICULTURAL CHEMISTRY 

490. Albumin. — The formula C 7 2Hii 2 Ni 8 S022 has been 
tentatively assigned to albumin. The albumin in meats 
ranges from 0.6 to 5 per cent. Liebig gives as a mean 
2.96 per cent. The lean meat of the pig as well as that 
of poultry contains a relatively large amount. Albumin 
is soluble in cold water, and is coagulated at a temperature 
of 1 5 7 to 163 F. and of 6o° to 75 C. Dilute acids con- 
vert albumins into acid albuminates, while alkalies produce 
alkali albuminates. The albuminates are proteids derived 
from albumins and other proteids by the action of acids 
or alkalies. 

491. Myosin. — Myosin is obtained from meat by 
extraction with a weak solution of common salt. The 
myosin dissolves in the salt solution and is precipitated by 
heat and chemicals (see Experiments 60 and 61). Myosin 
is a globulin, and in the living animal is largely in soluble 
forms. 

492. Syntonin has the same general relationship to 
myosin as dextrin has to starch. Dextrin is derived 
from starch and syntonin is derived from myosin. Synto- 
nin is an acid albuminate formed by the action of dilute 
acids. The amount of syntonin and myosin in meats is 
small, never exceeding, according to Hoffman, 2 or 3 per 
cent. 

493. Hemoglobin. — When fresh meat is soaked in 
cold water, the solution becomes red in color on account of 
the hemoglobin extracted. Hemoglobin is a proteid which 
imparts the red color to the blood and is coagulated 
by heat at a temperature of 128 to 132 F. There is 
enough of the various salts in the blood to dissolve some 
of the fibrin proteids which are precipitated at a tempera- 
ture of about 140 F. or 6o° C. 

494. Insoluble Proteids. — The larger portion of the 



COMPOSITION OF ANIMAL BODIES 353 

nitrogenous material of the muscles is in the form of 
insoluble muscular fiber. From 90 to 95 per cent or more 
of the total nitrogenous matter of fat-free lean meat is 
in insoluble forms. In the grains there are various 
insoluble proteids ; and in the different meats different 
kinds of insoluble proteids are present. Meats differ 
both as to the kinds and proportional amounts of the 
several proteids which they contain. 

495. Peptones. — When muscular fiber is acted upon 
by some ferments, peptones are produced. Only a small 
amount of peptones is present in meat. When meat is in 
cold storage to undergo the curing process before it is 
placed upon the market, the peptonizing process takes 
place to a slight extent. If the process is too long con- 
tinued, ptomaines, which are poisonous compounds, may 
develop. With meat of the best quality long curing is 
unnecessary. 

496. Keratin is an amide compound found in meat 
juices in small amounts ; 100 pounds of meat contain from 
0.07 to 0.32 of a pound. Like other amides, it possesses 
less food value than protein. Keratin, sarkin, and allied 
bodies are not coagulated by heat, but are gradually 
decomposed, and when meat is being cooked, pass off 
with characteristic odors. Keratin and sarkin are present 
in large amounts in beef extracts, and although they possess 
no direct food value, they impart palatability and are 
valuable mainly on this account 

497. Albuminoids, Gelatin. — When bone or muscular 
tissue is subjected to the action of boiling water, gelatin 
separates upon cooling and standing. Gelatin is quite 
different in chemical composition from albumin, muscular 
fiber, and other proteids. Hoffmeister gives the formula 
as Cio2Hi5iN 6 3 9. It contains no sulfur, while proteids 

2 A 



354 AGRICULTURAL CHEMISTRY 

contain from i to 2 per cent. Gelatin may prevent 
the rapid depletion of the protein of the body, but cannot 
take its place as a nutrient. The approximate amounts 
of the nitrogenous compounds in lean meat are given in 
the following table, from which it will be observed that 
only a small part is in the meat juices. 

The Nitrogenous Compounds of Meat. 



1. Proteids 



Per cent. 

Muscular fiber 12 to 18 

Albumin 0.5 to 2.0 

Myosin 0.4 to 0.6 

Syntonin 

2. Albuminoids Gelatin, etc 2.0 to 5.0 

(Keratin 0.07 to 0.34 
Sarkin 0.01 to 0.03 
Urea Traces 

4. Alkaloids (ptomaines) Occasionally traces 

498. Influence of Food upon the Composition of Ani- 
mal Bodies. — The nature of the food consumed has a 
noticeable effect upon the composition of the animal body. 
The food affects both the amount of meat produced and 
its composition. As a general rule, an unbalanced ration, 
particularly one with a large amount of non-nitrogenous 
compounds, produces flesh that is poor in circulatory 
proteids. But few systematic experiments have been 
made in regard to the influence of food upon the composi- 
tion of animal bodies. 

499. Composition of the Human Body. — Halliburton 
states that the human body contains 58.5 per cent water. 
The amount at different stages of life varies ; in later life, 
the body contains less than during youth. Water is 
present in all parts of the body ; enamel contains 2 per 
cent, the gray matter of the brain 85 to 86 per cent, 



COMPOSITION OF ANIMAL BODIES 355 

bone about 50 per cent, and muscle 75 per cent. The 
amount of fat varies between wide limits ; Moleschott 
states that normally it makes up from 4 to 5 per cent 
of the weight of the body. Adipose tissue contains about 
85, marrow 96, and nerves 22 per cent fat. Twenty- 
five per cent of the muscle is solid matter, of which 21 
per cent is proteid and albuminoid material, and 4 per 
cent are fat and nitrogenous extractive bodies. Mineral 
matter is present in small amounts combined with the 
muscular and other tissues and in solution in the various 
fluids and secretions. 



CHAPTER XXXVIII 
Rational Feeding of Men 

500. Similarity in the Principles of Human and Animal 
Feeding. — The rational feeding of men is founded upon 
the same principles as the rational feeding of animals. 
It is the object in each case to supply the body with the 
right kinds and amounts of nutrients to meet all its 
demands. It is not possible in either human or animal 
feeding to establish inflexible standards. 

501. Dietary Standards. — Some of the proposed 
standard rations call for about one fourth of a pound 
each of fat and protein and a pound of carbohydrates 
in the daily ration of a man at average muscular labor. 
Such a ration should yield about 3200 calories. The 
actual amount of nutrients consumed by laborers does 
not always conform to this standard. For example, 
studies show that the negro laborer in the South often, 
by choice, consumes about 0.1 pound per day of protein, 
while a well-fed mechanic frequently consumes over 
0.5 pound per day. While only tentative standards are 
proposed, experiments and dietary studies show that the 
best results are obtained in the feeding of men, as in the 
feeding of animals, when the ration conforms within 
reasonable limits to the standard. By a dietary standard 
is meant the approximate amounts of nutrients which 
the daily ration should contain. Such a standard as 
proposed by Atwater is as follows : 

356 



RATIONAL FEEDING OF MEN 357 

Carbohy- Fuel Nutri- 
Protein. Fat. drates. value. tive 
lb. lb. lb. Calories. Ratio. 

Man with little physical exercise 0.20 0.20 0.66 2450 5.5 

Man with light muscular work . 0.22 0.22 0.77 2800 5.7 
Man with moderate muscular 

work 0.28 0.28 0.99 3520 5.8 

Man with active muscular work 0.33 0.33 1.10 4060 5.6 

Man with hard muscular work . 0.39 0.55 1.43 5700 6.9 

502. Amounts of Foods consumed per Day. — In 

combining foods to form human rations, there should be, 
as in animal rations, a variety of foods, and no food article 
should be used in excess. The approximate amounts 
of foods consumed per day by a .man at average labor 
are as follows : 

Range. Average. 

Ounces. Pound. 

Bread 6 to 14 0.50 

Butter 2 to 5 0.12 

Potatoes 8 to 16 0.75 

Cheese 1 to 4 o. 1 2 

Beans 1 to 4 0.12 

Milk 8 to 3 2 

Sugar 2 to 5 0.20 

Meat 4 to 12 0.25 

Oatmeal 1 to 4 o. 1 2 

In a balanced ration, it is the aim to obtain from all of 
the foods approximately 0.25 pound each of fat and 
protein and a pound of carbohydrates. In case of severe 
work, larger amounts of nutrients, as indicated in the 
table, are necessary. The composition of human foods 
is given in the tables at the close of the chapter. 

To calculate the amounts of nutrients in fractions of 
a pound, the percentage composition of the food is mul- 
tiplied by the weight used, as in calculating animal rations 
(see Section 480). 



358 



AGRICULTURAL CHEMISTRY 



503. Calculating a Balanced Ration. — The various 
articles of food should be selected according to cost, 
nutritive value, purposes for which they are desired, 
amount and kind of work to be performed, and individual 
preferences. When bread, butter, milk, potatoes, sugar, 
oatmeal, corn meal, beef, ham, and eggs are to be combined 
to form a ration, such amounts are taken as will yield 
approximately 0.25 pound each of protein and fat, and 
a pound of carbohydrates. Such a combination would 
be as follows : 

Nutrients. 



Amount 

Foods. per day. Protein. 

Ounces. Pound. 

Ham 4 0.04 

Eggs (2) 0.03 

Bread : . . 8 0.05 

Butter 2 ... 

Potatoes 12 0.02 

Milk 16 0.04 

Sugar 2 

Oatmeal 2 0.02 

Beef (stew) 4 0.04 

Corn meal 4 0.02 

0.26 



Fat. 
Pound. 


Carbohy 
drates. 
Pound. 


Calories, 


O.09 




480 


0.02 




136 


O.OI 


O.28 


650 


O.I I 




450 




O.14 


285 


0.04 


O.05 


325 




O.I2 


200 


O.OI 


O.09 


230 


0.05 




250 


O.OI 


O.18 


420 



0.34 



0.86 



3426 



This ration contains 0.26 pound protein, 0.34 pound 
fat, 0.86 pound carbohydrates, and yields 3426 calories. 
While there is somewhat more fat and slightly less carbo- 
hydrates than the standard the ration is sufficiently 
near for all practical purposes. Some vegetables and 
fruits should be added, not so much with the object of 
increasing the nutrients as for the purpose of greater 
variety and palatability. In this ration, the nutrients 
are secured from a variety of sources, the largest amount 
of protein coming from the bread. About one third of 



RATIONAL FEEDING OF MEN 



359 



the protein is furnished by the meat, one fourth by the 
eggs and milk, while the balance comes from the vege- 
table foods. Bread, potatoes, corn meal, and sugar supply 
most of the carbohydrates, the two ounces of sugar 
supplying nearly 14 per cent. 

In combining foods to form balanced rations, meats, 
beans, cheese, milk, bread, and oatmeal supply protein, 
while pork, ham, bacon and other fat meats, butter, 
cheese, and milk supply the fats. Carbohydrates are 
provided liberally by bread, rice, corn meal, cereals, pota- 
toes, sugar, and vegetables. 

504. Comparative Cost and Value of Foods. — With 
human as with animal foods, the market price does not, 
as a rule, correspond with their nutritive value. When 
foods differ widely in cost, their relative values can be 




MiUC 




CHEESE 



BUTTER 



KOTctri-sq 



Fig. 100. — Comparative composition of milk, cheese, and butter 

approximately determined by comparing the amounts of 
nutrients which a given sum of money will procure in 
each case. The principle is the same as in the comparison 
of cost and value of animal foods, Section 483. 

In making comparisons, preference cannot be given to 
any single nutrient. In general, however, foods which 



360 AGRICULTURAL CHEMISTRY 

supply the largest amount of protein for a given sum of 
money are cheapest and most economical, provided there 
is no great difference in the amounts of fat and carbohy- 
drates. When there is but little difference in protein 
content, preference should be given to foods yielding the 
largest number of calories. 

In order to calculate the nutrients which can be pro- 
cured for a given sum of money, first determine the 
pounds of food, then multiply the weight by the percentage 
composition, using the figures in the tables. 

When round steak is 15 cents per pound and milk 5 
cents per quart, the amounts of nutrients which can be 
purchased for 1 5 cents are as follows : 

15 cents will buy 

Prote 
lbs. 

Round steak 1 

Milk 6 

Three quarts of milk or six pounds contain 0.03 pound 
more protein and 0.12 pound more fat and yield over 
1000 calories more than a pound of round steak costing 
the same. Milk at 5 cents per quart should be used 
liberally in the ration when steak is 15 cents or more 
per pound. It does not follow that meat should be 
entirely excluded from the ration in favor of milk, but the 
nutrients indicate that milk should be used in liberal 
amounts. 

Problem 1. — Calculate a balanced ration for a man at hard mus- 
cular labor and give the cost of the food articles required. 

Problem 2. — Calculate a ration for a man with little physical 
exercise, giving cost of ration. 

Problem 3. — Calculate the amounts of foods and the nutrients re- 
quired for a family of seven for ten days, three of the family to be 
considered as consuming each 0.8 as much as an adult. Calculate 



Protein, 
lb. 


Fat. 
lb. 


Carbo- 
hydrates, 
lb. 


Calories. 


O.18 


O.I2 




870 


0.2I 


O.24 


O.30 


I950 



RATIONAL FEEDING OF MEN 36 1 

the cost of the food. Then calculate, on the same basis, the prob- 
able amounts of food for one year with cost, adding 20 per cent 
additional for fluctuations in market prices and foods not included 
in the ten-day list. 

Problem 4. — How do beef and mutton compare as to nutrients 
when they are the same price per pound ? 

Problem 5. — Calculate the comparative amounts of nutrients 
that can be procured in cheese and loin steak at current market 
prices. 

Problem 6. — How do the nutrients in chicken at 16 cents per 
pound compare with those in round steak at 18 cents per pound ? 

Problem 7. — How does flour at 3^ cents per pound compare in 
nutritive value with a cereal breakfast food at 10 cents per pound, 
and having the same composition as whole wheat ? 

505. Factors Influencing Digestibility. — The factors 
discussed in Chapter XXXV, which influence the digesti- 
bility of animal foods, also influence the digestibility of 
human foods. The mechanical condition of the food 
and the method of preparation have a more pronounced 
effect in a human than in an animal ration. The term 
digestibility has, by some physiologists, been used to des- 
ignate ease of digestion rather than completeness of the 
process, foods which are easily digested and require but 
little work of the digestive tract being termed digestible, 
while those which require a larger amount of work are 
said to be indigestible. Some confusion has arisen from 
this use of the term digestible. For example, rice is 
frequently called a digestible food and cheese an indi- 
gestible food. Digestion experiments show that cheese 
is more completely digested than rice. A food which 
is easily digested is not necessarily completely digested. 
Variations in the digestive power of individuals influence 
digestibility ; for example, digestion experiments show 
differences of over 14 per cent in digestibility of the 
protein in a mixed ration of bread, milk, and beans. 



362 AGRICULTURAL CHEMISTRY 

There is a greater difference between individuals as to 
the ease of digestion than as to the completeness. Since 
digestion is largely a biochemical process, its complete- 
ness is necessarily influenced by the activity of the 
cells in the digestive tract. The combining of foods 
influences digestibility. For example, milk in a ration 
exerts a favorable influence upon the digestibility of 
the other foods with which it is combined. This is 
because of the presence in milk of enzymes or soluble 
ferments. Experiments show that 12.5 per cent of the 
protein in a sterile food, as toast, is capable of. being 
digested by the soluble ferments of milk. 

The method of cooking and preparing foods also exerts 
an influence upon their digestibility. Cooking changes 
both the physical and chemical composition of foods ; 
the cell walls of vegetables and cereals are broken and 
the starch granules ruptured, thus exposing them to more 
thorough action of the digestive fluids. Cooking influ- 
ences the ease or rapidity of digestion to a greater extent 
than it does the completeness of the process. The carbo- 
hydrates are favorably influenced by the action of heat, 
while, in some cases, prolonged heat may make the proteids 
less digestible. In pasteurized milk, for example, the 
proteids are slightly less digestible than in pure fresh 
milk, while in sterilized milk the digestibility is noticeably 
lessened. As in the case of animals, the mechanical 
condition of a food influences both the ease and the com- 
pleteness of the process. With persons of sedentary 
habits, the best results are secured when a small amount 
of some coarsely granulated food is present. A large 
amount of such foods is not suitable in the ration of a 
hard-working man because of lack of availability of the 
nutrients. 



RATIONAL FEEDING OF MEN 363 

506. Requisites of Ration. — Reasonable combina- 
tions should be made in forming balanced rations. A 
number of foods which are slow of digestion or require 
much intestinal work should not be combined. Neither 
should a number of foods which are easily digested and 
leave but little indigestible residue. Two foods which 
are either laxative or costive should not be combined. 
After formulating a ration, it should be critically examined 
to see if it satisfies the following conditions: (i) foods 
economical and suitable to the work to be performed, 
(2) foods combined so as to secure balanced work of the 
digestive tract, (3) foods not too laxative or too costive 
in effect, (4) requisite bulk, (5) sufficient amount of 
indigestible residue to dilute the waste products in the 
intestinal tract. 

507. Dietary Studies. — A dietary study considers the 
cost and amount of nutrients consumed by individuals 
and families. It is an investigation in which men are 
used and human foods are studied instead of farm animals 
and animal foods. Dietary studies show that frequently 
money is injudiciously spent in the purchase of high- 
priced foods which contain but a small amount of nutri- 
ents. In a dietary study, the amounts of nutrients in 
the foods exclusive of the refuse parts are determined, 
and from the weight of the foods, the nutrients contained 
are calculated, using the tables, or they are determined 
by chemical analysis. 

The purchasing of food is frequently done without 
regard to nutritive value. Erroneous ideas as to the 
value of foods are often the cause of extravagance in their 
purchase and use. As, for example, it has been claimed 
that the banana is as valuable as beef, and mushrooms 
have been erroneously called vegetable beefsteak. Many 



364 AGRICULTURAL CHEMISTRY 

other foods are assigned fictitious values. Too frequently, 
choice is made on the basis of palatability ; but cost of 
nutrients and kind of work to be performed should be 
considered as well as palatability. Dietary studies of 
the United States Department of Agriculture show that 
lack of knowledge in regard to the value of foods has 
frequently resulted in whole families being underfed, 
not from necessity, but from lack of judgment in the 
selection of foods. While it is not practicable or desirable 
to confine the ration to an absolute standard, dietary 
studies show that for long periods the best results are 
obtained when foods are combined so as to secure nutrients 
in approximately the amounts given as dietary standards. 
By means of a careful study of the dietary, it is possible 
to reduce the cost of food without impairing its nutritive 
value, and in many cases, as the cost is decreased, the 
nutritive value is increased. 

508. Chemical Changes in the Cooking of Foods. — The 
chemical changes which take place in cooking are brought 
about by the action of heat, water, and ferments, and occa- 
sionally by the use of chemicals. ' The various compounds 
of which foods are composed, namely, carbohydrates, 
proteids, and fats, are all susceptible to the action of these 
agencies, and the chemical changes which they undergo 
are briefly discussed in Chapters XXIII and XXIV, 
treating of the composition of the nitrogenous and non- 
nitrogenous compounds. Some of the changes are physical 
rather than chemical in character. 

All of the different nutrients of foods are influenced 
by the action of heat. Starch, in the presence of water 
and heat, undergoes partial hydration, so that the material 
is in condition both chemically and mechanically to 
undergo readily inversion changes. In the cooking and 



RATIONAL FEEDING OF MEN 



365 



preparation of foods, starch rarely undergoes more than 
the hydration change. In bread-making, for example, 
only a small portion of the original starch is converted 
into soluble forms. 

The action of heat upon cellulose and cellular tissue 




FJBE 



Fig. ioi. — Comparative composition of raw and baked beans. 

is mechanical rather than chemical. The mass is partially 
disintegrated, and in the case of some of the cellulose, 
hydration takes place to a limited extent. Human foods, 
however, contain comparatively little of the cellulose 
group of compounds. The sugars are partially caro- 
melized by heat, provided it is sufficiently intense, but in 
ordinary cooking operations, they undergo little or no 
chemical change unless associated with acids, alkalies, 
or ferment bodies, in which case they may be converted 
into a number of chemical products. 

In the cooking of fruits, as the baking of apples, a 
portion of the levulose is partially carbonized. If the 
fruit is not fully matured, the pectose substances or jellies 
are converted into a more soluble condition by the action 
of heat. When heat is sufficiently intense, the essential 
or volatile oils are expelled. Fats, as a class, undergo 



366 AGRICULTURAL CHEMISTRY 

slight oxidation changes by the action of heat. For 
example, the fat extracted from the bread is different in 
character from that in the original flour. It is darker in 
color, and chemical tests show that it is slightly oxidized. 

Heat causes the proteids to undergo more complex 
changes than any other class of nutrients. The soluble 
albumins are coagulated, the globulins also are coagulated, 
and if the heat is sufficiently intense, molecular changes 
take place, in which the elements composing the proteid 
molecule are rearranged, forming, practically, a new 
molecule with different chemical and physical properties. 
Since the proteid compounds contain fatty acid radicals, 
carbohydrate-like bodies, amides, and radicals of other 
compounds, a number of chemical changes may take 
place, varying with the degree of heat employed. 

The chemical changes which occur in the process 
of cooking influence, to a limited extent, the digestibility 
of the foods. As a rule, the total digestibility of the 
carbohydrate nutrients is changed but little by the action 
of heat. For example, experiments show that the carbo- 
hydrates in toast are no more completely digested than 
the carbohydrates in bread, but the action of heat in the 
preparation of toast produces chemical and physical 
changes which render the nutrients more susceptible 
to the action of the digestive fluids, and while toast is no 
more completely digested than bread, it is more readily 
acted upon by the digestive fluids. Prolonged heat has 
a tendency to decrease the digestibility of the proteid 
compounds as a class. In toast, the proteid nutrients 
are slightly less digestible than in bread. 

In general, it can be said that cooking affects ease of 
digestion rather than completeness of the process, that 
the carbohydrates are practically as digestible before the 



RATIONAL FEEDING OF MEN 367 

action of heat as after, and that the proteids are slightly- 
less digestible after the action of prolonged heat. Experi- 
ments in the feeding of animals show that when foods 
are cooked, the total digestibility of the nutrients is not 
increased, and in some cases, a smaller amount of nutrients 
was absorbed after cooking than before. This does not 
mean that the cooking of foods is undesirable, because 
ease of digestion is equally as important as completeness 
of digestion. Also cooking sterilizes the food, which 
is desirable. Many foods, if consumed uncooked, would 
be unwholesome because of the presence of ferment 
bodies or poisonous compounds as ptomaines. When 
acted upon by heat, the ferment bodies are destroyed and 
the ptomaine compounds decomposed. 

When salt, soda, or other chemicals are used, chemical 
changes, to a limited extent, take place. Soda, for 
example, combines with the proteid compounds of foods, 
forming alkali proteids, and the acids form acid proteids. 
In cooking and preparing foods, the physical changes 
which occur often precede and are necessary to the 
chemical changes. In boiling potatoes, for example, 
heat changes the physical character of the cells but does 
not alter the solubility of the starch. The albumin is 
coagulated, and small amounts of the mineral compounds 
and other bodies are extracted. In cooking of some of 
the cereals, as oatmeal, if the process is continued for only 
a few minutes, the starch is not acted upon to any appre- 
ciable extent because of the gelatinous proteids which 
protect the starch particles. If the cooking is continued 
for three or four hours, they are disintegrated, the starch 
cells are ruptured, and instead of masses of starch, small 
particles of disintegrated starch may be observed. This 
starch is partially hydrated. Oatmeal cooked in the 



3 68 



AGRICULTURAL CHEMISTRY 




Frotein. 

B 
■ F at. 



j&L, 



two ways, for a few minutes, and for four hours, contains 
practically the same percentage amount of total starch. 

In the one case, however, 
the starch is in large masses, 
unruptured and unaltered, 
while in the other, the starch 
masses have been ruptured, 
the particles are in a finer 
state of division, and are 
partially hydrated. Oat- 
meal which has been cooked 
for only a few minutes 
does not readily undergo 
digestion, but four hours' 
cooking produces physical 
and intermediate chemical 
changes that cause the 
starch to yield readily to 
the action of the diastase ferment. 

In cooking meats, the heat liquefies a portion of the 
fat and oxidizes a portion of that exposed to the air, 
while the proteids undergo complex molecular changes. 
In cooking and preparing foods, it should be the object 
to bring about physical rather than chemical changes. 
Cooking influences the ease rather than the completeness 
of digestion. 

509. Refuse and Waste Matters. — Nearly all foods 
contain some refuse material which cannot be consumed 
as food. Of average meat, as purchased in the market, 
from 7 to 56 per cent is refuse ; round steak has least, 
while shank has most. Tables showing the average 
amounts of refuse in meats are given at the close of the 
chapter. The waste of a food is frequently enough to 



Fig. 102. — Composition of bread. 



RATIONAL FEEDING OF MEN 369 

make the nutrients of the edible portion quite expensive 
even in apparently cheap foods. In vegetables, the 
refuse ranges from 15 to 50 per cent. About 15 per cent 
of the weight of potatoes is lost as parings; of fresh 
peas, one half of the weight is pods, and of squash, one 
half the weight is rind and seeds. In calculating the 
nutrients of foods, the refuse and waste parts should be 
considered, as there is nearly always a smaller percentage 
amount of nutrients in the edible portion than in the 
food as purchased. 

510. Loss of Nutrients in the Preparation of Foods. — 
In the cooking of vegetables, as potatoes, carrots, and 
cabbage, some of the soluble nutrients, as albumin, sugar, 
and mineral matter, are extracted and lost in the water. 
In the case of potatoes, experiments show that over 57 
per cent of the total nitrogenous matter is extracted and 
lost when potatoes are cut in small pieces and soaked in 
cold water. When the cleaned, unpeeled potatoes were 
placed directly in hot water, the loss amounted to only 
1 per cent. In the case of carrots and cabbage, the 
loss is great if the pieces are small and much water is 
used. There need not be much loss of nutrients incident 
to cooking meats, provided mechanical losses are avoided. 
In the boiling of meat, there is a decrease in weight of 
about 30 per cent, due largely to loss of water. About 
5 per cent of proteid matter is extracted, also 13 to 15 
per cent of fat and 51 per cent of mineral matter. With 
small pieces of meat, the total loss of weight may be over 
50 per cent. The amount of nutrients dissolved varies 
with the size of the pieces. From experiments made at 
the University of Illinois, there does not appear to be 
any great difference in the amount of nutrients extracted 
from meats by hot or cold water. If the broth is utilized 

2B 



370 AGRICULTURAL CHEMISTRY 

for soup, the nutrients extracted during cooking are not 
lost. 

Sir. Mineral Matter in a Ration. — In the calculation 
of human as well as animal rations, the mineral content 
of the food is not considered along with the other nutrients. 
This is not because the mineral nutrients are of insig- 
nificant value, but because nearly all combinations of 
foods contain sufficient, both in amount and variety, for 
nutritive purposes. Phosphates, compounds of iron, 
potassium, and magnesium are required only in compara- 
tively small amounts. It is estimated that with a man 
at hard labor from 2 to 3.5 grams per day of phosphoric 
acid are eliminated through the kidneys. Since this 
includes all of the soluble mineral phosphates of the food, 
and not all of those are used for functional purposes, it 
is not necessary that the food should contain even 2 to 
3.5 grams of available phosphates per day. A ration 
consisting entirely of white bread contains enough phos- 
phates to supply the body and establish a phosphate 
equilibrium. An average daily ration of mixed foods 
contains from 5 to 8 grams or more. Meats and nearly 
all animal foods contain about 1 per cent of mineral 
matter, of which about half is phosphoric acid. Milk 
and eggs contain phosphates and mineral matter in liberal 
amounts. In a mixed ration of three or more food articles, 
there is always enough phosphates and mineral matter 
for purposes of nutrition. A part of the excess of phos- 
phates in a ration is eliminated through the kidneys. 
The feces also contain phosphoric acid. Inability of 
the organs to assimilate phosphates, due to malnutrition 
and lack of available forms of other nutrients, is more 
frequently a source of trouble than lack of phosphates 
in the food. 



RATIONAL FEEDING OF MEN 37 1 

" It is evident, however, that a large part of the mineral 
constituents of cereals is not required for nourishment 
of the body. Feeding experiments have confirmed this 
theoretical view, and the ash of food materials has the 
lowest coefficient of digestion of any constituents thereof 
with the possible exception of cellulose. 

" In grinding and reducing to merchantable flour a 
considerable portion, as a rule more than half, of the 
mineral ingredients is removed in the waste products 
of the meal. Enough is left, however, not only to supply 
the need of the body for mineral constituents but also 
for condimentary purposes." (H. W. Wiley, Bui. 13, 
Part 9, Div. Chem., U. S. Dept. Agr.) 

It is estimated that in the ration of an adult, about 20 
grams per day of sodium chlorid are necessary. This 
compound takes an important part in nutrition and is 
a normal constituent of all the fluids of the body. 

512. Digestibility of Foods. — The digestibility of 
foods is a subject which belongs for investigation alike 
to the chemist, the physiologist, and the bacteriologist. 
The physiologist considers the structure of the digestive 
tract and the functions of the various organs ; the chemist 
studies the chemical changes which occur while the food 
is undergoing digestion, the completeness of the digestion 
process, and the extent to which the nutrients of the 
food are made available to the body ; the bacteriologist 
deals with the ferment bodies which assist in the process 
of digestion. 

513. Digestibility of Meats. — The nutrients of meats, 
particularly the fats and proteids, are more completely 
digested than the same classes of nutrients in vegetables. 
From 93 to 95 per cent or more of the proteids and fats 
from foods of animal origin are completely digested, 



372 AGRICULTURAL CHEMISTRY 

while of vegetables not more than 85 per cent of the 
proteids are completely digested except in the case of 
finely ground flour. Meats are concentrated foods, as 
they furnish large amounts of nutrients in digestible forms. 
There is less difference in the completeness with which 
the various meats are digested than in the ease of digestion. 
Some meats, as pork, veal, and mutton, which are called 
indigestible, are slow of digestion but are quite completely 
digested. The nutrients of meats can, for all practical 
purposes, be considered entirely digestible. 

514. Digestibility of Vegetable Foods. — Vegetable 
foods are less completely digestible than animal foods. 
The larger the amount of cellulose or fiber, the less com- 
pletely digested is the food. Only a very small amount 
of the cellulose, even hydra ted cellulose, of human foods 
is available to the body. In many vegetables the nutrients 
are inclosed in cellular tissue, and thus, to a certain extent, 
are protected from the solvent action of the digestive 
fluids. The starches and carbohydrates of vegetables are 
more completely digested than the proteids. Frequently 
95 per cent of the starch and only 80 per cent or less of 
the proteids are digested. There is a wide range in the 
digestibility of the nutrients of vegetable foods. The 
nutrients of fruits are, as a rule, more completely digested 
than those from other vegetable sources, but fruits contain 
little nutritive material. 

515. Relation of Food to Health. — Since the function 
of food is to supply the body with nourishment, the 
subjects of food and health are necessarily closely related. 
If too long continued, either an abnormally large or too 
scant an amount of food affects the health. And not 
only is the amount important to health but also the 
quality of the food, as nature of nutrients and sanitary 



RATIONAL FEEDING OF MEN * 373 

condition. Many diseases result from malnutrition, 
while many others are caused by the use of foods in an 
unsanitary condition. Food may cause disease either 
on account of its being unsanitary or because of an exces- 
sive or deficient amount of nutrients, or because the 
nutrients are unbalanced. 



374 



AGRICULTURAL CHEMISTRY 



Composition of Human Foods. 

(From Bulletins Nos. 28 and 34, Office of Experiment Stations.) 



Kind of Food. 



Beef — Chuck ribs 

Edible portion 

As purchased 

Loin : 

Edible portion 

As purchased 

Neck: 

Edible portion 

As purchased 

Ribs: 

Edible portion 

As purchased 

Round : 

Edible portion 

As purchased 

Rump : 

Edible portion 

As purchased 

Shank, fore : 

Edible portion 

As purchased 

Shank, hind : 

Edible portion 

As purchased 

Fore quarter : 

Edible portion 

As purchased 

Hind quarter : 
Edible portion 



P4 



13.8 



13.0 



27.6 



20.8 



7-7 



21.4 



36.9 



53-9 



19.4 



NuTRrENTS. 



Ph 



57 
49 

60 

52 

63 
45 

55 
43 

65 
60 

56 
44 

67 

42 

67 
3i 

61 
49 



61.0 






> 3Ph 



42.7 
36.9 

39-5 
34-4 

36.6 
26.5 

44.6 
35-4 

34-2 
31.6 

43-3 
34-i 

32.1 
20.2 

32.2 
14.8 

38-6 
3i-i 

39-o 






Ph p., 



17.4 
15.0 

18.3 

15-9 

19.2 
13-9 

16.9 

13-4 

19.7 
18.1 

16.8 
13.2 

19.6 
12.3 

19.8 
9.1 

17-5 
14.1 

18.0 



^ 53 

Ph 



24.4 
21. 1 

20.2 
17.6 

16.5 

11. 9 

26.8 
21.3 

13-5 
12.6 

25.6 
20.2 

11. 6 

7-3 

n-5 

5-3 

20.2 
16.3 

20.1 



0.9 

0.8 

1.0 
0.9 

0.9 
0.7 

0.9 
0.7 

1.0 

0.9 

0.9 
0.7 

0.9 
0.6 

0.9 
0.4 

0.9 

0.7 

0.9 



> 

fa O 



1355 

1 1 70 

1190 
1040 

1055 

760 

1445 
1150 

935 
870 

1395 
1095 

855 
535 

855 
395 

1180 
95o 

1815 



RATIONAL FEEDING OF MEN 



375 



Composition of Human Foods (Continued). 



Kind of Food. 



Beef (Contin'd) : 
As purchased 

Cooked, corned, and 
canned : 
As purchased 

Dried and smoked : 
As purchased 

Veal — Leg, whole : 

Edible portion 

As purchased 

Rump : 

Edible portion 

As purchased 

Fore quarter : 

Edible portion 

As purchased 

Hind quarter : 

Edible portion 

As purchased 

Lamb — Leg, hind : 

Edible portion 

As purchased 

Loin : 

Edible portion 

As purchased 

Neck: 

Edible portion 

As purchased 

Shoulder : 

Edible portion 

As purchased 



P>H 



15-8 



15-6 



30.2 



24-5 



20.7 



17.4 



14.8 



17.7 



20.3 



NlITRDSNTS. 



5i-3 

53-i 
50.8 

70.4 
59-4 

62.6 
43-7 

71.7 
54-2 

70.9 
56.2 



4) • 

£ y c 

•22 S "- 1 

> 3 Oh 



32.9 

46.9 
4Q.2 

29.6 
25.O 

37-4 
26.1 

28.3 
21.3 

29.1 
23.1 



o "5 



Ph o< 



63-9 


36.1 


52.9 


29.7 


53-i 


46.9 


45-3 


39-9 


56.7 


43-3 


46.7 


35-6 


51.8 


48.2 


4i-3 


38.4 



15.2 

28.5 
31.8 

20.1 
16.9 

20.1 
14.0 

19.4 

14.6 

19.8 

15-7 

18.5 
15.2 

17.6 
15.0 

17-5 
14.4 

17-5 
14.0 



f* S3 
Ph 



< u 



I7.0 
I4.O 

6.8 

8.4 

7.2 

16.2 
n-3 

8.0 
6.0 

8-3 
6.6 

16.5 
13.6 

28.3 
24.1 

24.8 
20.4 

29.7 
23.6 



S.8 
a g 



0.7 



4.4 



I.I 
0.9 

I.I 

0.8 

0.9 

0.7 

I.O 

O.8 

I.I 
O.9 

I.O 

0.8 

I.O 

0.8 



IOOO 



II20 
845 

730 
620 

I055 

735 

700 
525 

720 
57o 

1040 
855 

1520 
1295 

1375 
1130 



1.0 

0.8 



1580 
125s 



376 



AGRICULTURAL CHEMISTRY 



Composition of Human Foods {Continued). 



Kind of Food. 



Mutton — Leg, hind : 

Edible portion 

As purchased 

Loin : 

Edible portion 

As purchased 

Neck: 

Edible portion 

As purchased 

Shoulder : 

Edible portion 

As purchased 

Fore quarter : 

Edible portion 

As purchased 

Hind quarter : 

Edible portion 

As purchased 

Side, without tal- 
low : 

Edible portion 

As purchased 

Pork — Flank : 

Edible portion 

As purchased 

Ham, smoked : 

Edible portion 

As purchased 

Shoulder, fresh : 

Edible portion 

As purchased 



18.0 



J5-3 



28.4 



21. 



21. 1 



16.7 



19.2 



71.2 



14.4 



46.6 



fa 



62.8 
5i-4 

50. 1 
42.2 

58.2 
41.6 

61.9 

48.5 

5i.7 
40.6 

54-8 
45-6 



53-i 
42.9 

59-o 
17.0 

40.7 
34-9 

57-5 
30-4 



Nutrients. 



> 5 fa 



37-2 

30.6 

49.9 

42.5 

41.8 

30. o 

38.1 

29.8 

48.3 
38.3 

45-2 
37-7 



46.9 
37-9 

41.0 
11. 8 

59-3 
50.7 

42.5 
23.0 



e a 



fa fa 



18.2 
14.9 

15.9 
13.2 

16.3 

11. 7 

17-3 
13-5 

15.0 
11. 9 

16.2 
13-5 



15-4 
12.5 

17.8 
5-i 

15-5 
13-3 

15.6 
8-3 



18.0 
14.9 

33-2 
28.6 

24-5 
17.6 

19.9 
15.6 

32.4 
25-7 

28.2 
23-5 



30-7 
24.7 

22.2 
6.4 

39-i 
33-4 

26.1 
14.3 



D. o 

% "^ 
.2CJ 

> . 

a a 

fa 5 

a. 



1.0 
0.8 

0.8 
0.7 

1.0 

0.7 

0.9 

0.7 

0.9 
0.7 

0.8 
0.7 



I IOO 

905 

169s 
1450 

1335 

960 

1160 
910 

164s 
1305 

1490 
1245 



0.7 
0.7 

1.0 

o-3 

4-7 
4.0 



1580 
127s 

1265 
365 

1940 
1655 



0.8 1390 
0.4 760 



RATIONAL FEEDING OF MEN 



377 



Composition of Human Foods (Continued). 



Kind of Food. 



Pork (Contin'd) : 

Salt, clear fat : 
As purchased 

Salt, lean ends : 

Edible portion 

As purchased 

Bacon, smoked : 

Edible portion 

As purchased 

Side : 

Edible portion 

As purchased 

Poultry — Chicken : 

Edible portion 

As purchased 

Turkey : 

Edible portion 

As purchased 

Fish, fresh — Cod, 
dried : 

Edible portion 

As purchased 

Mackerel, ent. rem'd : 

Edible portion 

As purchased 

Salmon, Cal., sections: 

Edible portion 

As purchased 

Salmon trout, whole : 

Edible portion 

As purchased 



t>i 



II. 2 



8.0 



II. 2 



34-8 



22.7 



29.9 



40.7 



10.3 



56.3 



^ c 

3! 2 




Nutrients. 




Water-free 
substance. 
Per cent. 


fafL, 


4-1 

c 

fa 


. c 
< w, 

V 
fa 


7-3 


92.7 


1.8 


87.2 


3-7 


19.9 


80.I 


7-3 


67.1 


5-7 


17.6 


71.2 


6-5 


59-6 


5-i 


18.2 


81.8 


10.0 


67.2 


4.6 


16.8 


75-2 


9.2 


61.8 


4.2 


29.4 


70.6 


8-5 


61.7 


0.4 


26.1 


62.7 


7-5 


54-8 


0.4 


74.2 


25.8 


22.8 


1.8 


1.2 


48.5 


16.7 


14.8 


1.1 


0.8 


55-5 


44-5 


20.6 


22.9 


1.0 


42.4 


34-9 


15-7 


18.4 


0.8 


82.6 


17.4 


15-8 


0.4 


1.2 


58.5 


11. 6 


10.6 


0.2 


0.8 


73-4 


26.6 


18.2 


7-i 


i-3 


43-7 


15-6 


11. 4 


3-5 


0.7 


63.6 


36.4 


17-5 


17.9 


1.0 


57-9 


31-8 


16.1 


14.8 


0.9 


69.1 


3o-9 


18.2 


11. 4 


i-3 


30.0 


*3-7 


7-7 


5-4 


0.6 



u .u 



> . 

o a 

P 3 

fa o 



3715 

2965 
2635 



2780 

2760 
2455 

500 
325 

I350 
1070 



310 
205 

640 
360 

1080 
925 

820 
98S 



378 



AGRICULTURAL CHEMISTRY 



Composition of Human Foods (Continued). 



Kind of Food. 



Fish (Contin'd) : 

Trout, brook, whole : 

Edible portion 

As purchased 

Fish, pres'v'd, Cod, 
salt : 

Edible portion 

As purchased 

Mackerel, salt : 

Edible portion 

As purchased 

Salmon, canned, as pur- 
chased 

Sardines, canned, as 
purchased 

Shell fish, clams, 
round : 

Edible portion 

As purchased 

Oysters, "solids," 
purchased 

Dairy Products 
Cheese — Cheddar . 

Butter 

1 Milk 

1 Cream 

Eggs: 

In shell 

Edible portion 



as 






Pi 



Ph 



48.I 



24.9 



22.9 



67-5 



13-7 



ph 



77-8 
40.4 

53-6 
40.3 

42.2 

32-5 

64.5 
56.4 



86.2 
28.0 



33-o 
13.0 
87.0 



63.1 
73-8 



Nutrients. 



9?,A 



^ -2 £ 



22.2 

"•5 



46.4 
34-8 

57-8 
44.6 

35-5 
43-6 

13-8 
4-5 

11. 7 

67.0 
87.0 
13.0 



23.2 
26.2 



2 >- 

Ph Ph 



18.9 
9-8 



21.4 
l6.0 

22.0 
I7.0 

20.I 

2 5-3 

6.5 
2.1 

6.1 

28.0 
0.5 

3-5 
2-5 

12. i 
14.9 



Ph 



2.1 
I.I 



O.4 
O.4 

22.6 
17.4 

11. 6 
12.7 



0.4 

O.I 

1.4 

35-o 

85.0 

4.0 

20.0 

10.2 
10.5 



Ph 



1.2 

O.6 



24.6 
18.4 

I3.2 
I0.2 

2.4 

5-6 



2.7 
0.9 

0.9 

4.0 

i-5 

0.7 

0.5 

0.9 
0.8 



a o 
.Scj 

a! 
> . 

— ~o 

r? 3 



440 
230 



410 

315 

1360 
1050 

890 

IOIO 



21S 

65 

235 
1999 

3600 

323 



655 

721 



1 Milk also contains 4.8 per cent carbohydrates. The fat content 
of cream ranges from 10 to 30 per cent. 



RATIONAL FEEDING OF MEN 



379 



Composition of Human Foods {Continued). 



Kind of Food. 



Wheat flours, meals, 
etc: 
1 Roller process flour . . 
Spring wheat flour . . . . 
Winter wheat flour 

Buckwheat flour 

Corn meal, bolted 

Oatmeal 

Rice 

Rice, boiled 

1 White bread 

1 Graham bread 

Crackers 

Sugar, granulated 

Sugar, maple 

Vegetables — Aspara- 
gus : 
As purchased 

Beans, dried : 
As purchased 

Beets : 

Edible portion 

As purchased 

Cabbage : 

Edible portion 

As purchased 

Carrots : 

Edible portion 

As purchased 



X 



20.0 



I5.0 



20.0 



I2.9 

11. 6 
12.5 

14.3 

12.9 

7.2 
12.4 

52.7 

31.0 

32.2 

8.2 



94.0 

13.2 

87.6 
70.0 

90.3 
76.8 

88.2 

70.5 



.5 c 



Ph Ph 



12.2 
II. 8 
IO.4 

6.1 
8.9 
15-6 
7.8 
5-o 
9.9 

9-5 
10.7 



22.3 

1.6 
i-3 

2.1 
1.8 

1.1 
0.9 



Ph 



1.0 
I.I 
1.0 
1.0 

2.2 

7-3 

0.4 

O.I 

1.4 

2.5 
9.9 



0.2 
1.8 

O.I 
O.I 

0.4 

o-3 

0.4 
°-3 



-^ PL. 

re 
U 



74-3 
75-o 
75-6 
77.2 

7S-i 
68.0 
79.0 
41.9 
57-i 
54-7 
68.8 
98.0 
82.8 



3-3 
59-i 

9.6 

7-7 

5-8 
4.9 

9.2 
7-4 



< H 



in 

v •£ 

a o 

a 
> . 



°-5 

0.5 
0.5 
1.4 
0.9 
1.9 
0.4 

o-3 
0.6 
1.1 
2.4 



0.7 
3-6 

1.1 
0.9 

1.4 
1.2 

1.1 

0.9 



1665 
1660 
1640 
1590 

i6S5 
i860 
1630 

875 
1306 

1895 
1600 

1540 



105 

i59o 

210 
170 

165 
140 

210 
170 



From Minnesota analyses. 



3 8o 



AGRICULTURAL CHEMISTRY 



Composition of Human Foods (Continued). 



Kind of Foods. 



Vegetables (Contin'd) 

Parsnips : 

Edible portion 

As purchased 

Peas, dried : 
As purchased 

Peas, green : 

Edible portion 

As purchased 

Potatoes, raw : 

Edible portion 

As purchased 

Potatoes, sweet : 

Edible portion 

As purchased 

Squash : 

Edible portion 

As purchased 

Turnips : 

Edible portion 

As purchased 

Tomatoes : 

Edible portion 

Green corn 

Cucumber 

Spinach 

Sauerkraut 



^2 <-> 



Ph 



20. 



50.0 



15.O 



15.O 



50.0 



30.0 



Pi 



79-9 
63-9 

10.8 

78.1 
39-o 

78.9 
67.1 

69-3 

58.9 

86.5 
43-3 

88.9 
62.2 

96.0 
81.3 
96.0 
92.4 
86.3 



Ph (X, 



i-7 
*3 

24.1 

4.4 
2.2 

2.1 
1.8 

1.8 
i-5 

1.6 
0.8 

1.4 
1.0 

0.8 
2.8 
0.8 
2.1 
i-5 



Ph 



0.6 

°-5 



0.5 
°-3 

0.1 

O.I 

0.7 
0.6 

0.6 

°-3 
0.2 

O.I 

0.4 

I.I 

0.2 

0.5 
0.8 



a .J 

1? « 

•s <~ 

O <U 

-° Oh 

u 



16.1 

12.9 

61.5 

16.1 
8.0 

18.0 
15.3 

27.1 

23.1 

10.4 

5-2 

8.7 

6.1 

2-5 
14.1 

2-5 
3-i 
4.4 



Ph 



5U 



1.7 
1.4 

2-5 

0.9 
0.5 

0.9 
0.7 

I.I 

0.9 

0.9 
0.4 

0.8 
0.6 

°-3 

0.7 

0.5 
1.9 
7.0 



553 

528 

1640 

400 
200 

380 
325 

565 
480 

245 
125 

195 
135 

80 
360 

70 
120 
145 



INDEX 



Acid, citric 197 

hydrochloric .... 76-79 

malic 196 

oxalic 197 

phosphoric 90 

salts 72 

silicic 98 

sulfuric 94 

tannic 197 

tartasic 196 

Acids 69 

basicity of 72 

fatty 191 

naming of 71 

organic 195 

Aerobic ferments 319 

Air 63, 68 

a mechanical mixture ... 63 

ammonium compounds of . . 65 

as plant food 74 

carbon dioxid of ... . 63, 65 

impurities in 67 

liquid 67 



moisture in 

Albumin in meat 

Albumins 

Albuminates 

Albuminoids 

food value of . . 

Alfalfa 

Aliphatic series 

Alkaloids 

Allotropism 

Aluminum 

in plants . . . . 

Alums 

Amides 

food value . . . . 

occurrence in animals . 

plants . 



215- 



217- 



66 
352 
208 
209 
217 
216 

253 
108 
220 
47 
138 
161 
138 
220 
221 
218 
217 I 



Ammonia 84 

properties of ... 85 

uses of 85 

Ammonium compounds in air . 65 

Anaerobic ferments 305 

Anhydrids 86 

Animal bodies, composition of 348-355 
fat in .... 349 
mineral matter in 348 
nitrogenous mat- 
ter of . . . 349 
Animal life, chemical change . . 8 

Antitoxins 309 

Apatite 87, 130 

Apparatus, names of ... 17, 20 

Apples 300 

Argon 67 

Aromatic series 108 

Arsenic, occurrence 144 

poisoning 145 

Ash determination 154 

Ash elements, essential . . . . 155 

of animal bodies .... 348 

of plants 155-167 

composition of . . 167 

Atomic weight 14 

table of ... . 12 

Atoms 6 

Bacteria, disease-producing . . 309 

Balanced rations 328 

calculation of . 338 

Barley 280, 290 

grading of 287 

Bases 69 

naming of 71 

Beans 282 

Beef production, foods for . . . 332 

Benzine 103 

Beri beri 210 



38i 



382 



INDEX 



Bessemer process 135 

Blast-furnace 134 

Bleaching-powder 130 

Bordeaux mixture 142 

Bread 321,371 

Brick 139 

British thermal units .... no 

Bromus Inermis 252 

Buckwheat 281 

Burette 73 

Calcium 128 

carbonate 128 

chlorid 130 

compounds 128 

hydroxid 129 

hypochlorite . . . . 130 

in plants 159 

oxid 129 

phosphate 130 

sulfate 130 

Caloric value of rations . . . 341 

Calorie 110,313 

Calorimeter 314 

Candle, chemistry of ... . 50 

power 107 

Capillarity of plant tissue . . . 229 

Carbids 109 

Carbohydrates 169-188 

digestibility of . . 319 

Carbon 45~54 

a reducing agent ... 47 

compounds 52 

a decolorizer 51 

a deodorizer 51 

dioxid 102 

in air 63 

test for .... 129 

disulfid 109 

monoxid 103 

occurrence 45 

oxids of 129 

preparation of ... . 45 

properties of 4° 

role in plant and animal 

life 53 

Carbonates 102 

Carrots 3°° 

Cellulose 170-173 



Cellulose, chemical properties of 
food value of . . . 
function of 
physical properties of 

Chemical affinity 

analysis .... 
changes .... 
properties defined . 

Chemistry 

Chlorids 

Chlorin 78 

family . 80 

preparation 78 

properties 79 

Chlorophyll 231-234 

function of ... . 233 

production . . . . 232 

Citric acid 197 



171 
171 
171 
170 

7 
8 

3 
io-n 

4 
. 80 



100 

28 

247 

236 

237 
252 
236 

47 
16 



Clay 

Cleaning apparatus .... 

Climate and plant growth . . 

Clover, composition of . . . 

early and late cut . . 

hay 

rapidity of growth 

Coal 

Combination of elements . . 

Combustion . 48 

products of ... 51 

spontaneous ... 50 

Composition of matter .... 3-8 

Compounds 7 

Cooking of foods, changes during 

carbohydrates . . . 364 

fats 365 

proteids 366 

losses during .... 369 

Copper 14 1 

compounds .... 141-142 

sulfate 14 1 

Corks, perforation of .... 22 
Corn (see maize). 

flour 278 

fodder 254 

Cottonseed cake and meal . . 295 

Creosote 109 

Crop growth and soils .... 246 
Crops, improvement of ... . 249 
Crude fiber 172 



INDEX 



383 



Crude protein 213 

Crystallization, water of . . . 5° 
Cyanids i°9 

Dairy cows, food for .... 335 

requirements of . . 334 

Definite proportion, law of . . 15 

Dextrin J 78 

Dextrose x ^ 2 

chemical and physical 

properties of ... 182 

Dialysis 99 

Dietary standards 35° 

studies . . . . • • 363 

Digestibility, factors influencing 361 
influence of cooking 

upon .... 364 

Digestible nutrients 326 

in fodders and 

grains 346, 347 

Digestion, a biochemical process 311 
chemistry of . .311-328 

coefficients . . . • 3 11 

not constant 323 

experiments . . . . 3 11 

factors influencing . 320 

Disease, air 67 

and water supply . 56-60 

Double salts . 72 

Dry matter 15 1 

Elastin 216 

Elements and compounds, prop- 
erties 6-18 

classification of . . . 69 
combination of . . 12, 18 

cycle of 114 

Energy, available, of foods . . 316 
net, of foods . . . . 317 

Epsom salt 132 

Equations 11 5-1 18 

for classroom . . n 9-1 20 

Essential oils 198-200 

food value . . . 200 
synthetic produc- 
tion of ... . 200 
Ether extract 194 



Fat in animal bodies 
Fats 



349 
-195 



Fats, amounts of, in foods . . 193 

chemical properties . . . 189 

digestion of 316 

food value of 192 

formation in plants . . . 188 

heat from 192 

physical properties . . 189 

Fatty acids 192 

Feeding of animals .... 328-348 
and sanitary conditions 344 

standards 344 

stuffs, inspection of . . 297 

Feldspar 100 

Fermentation 305-310 

conditions necessary 
for . . . 
Ferments, aerobic . . . 
anaerobic . . 
and bread-making 
in butter- and cheese- 
making 
disease-producing . 
and food digestion 

preservation 
in seeds . . 
soils . . 
insoluble . 
soluble . . 
Fertilizers, phosphate . 
Fiber, crude .... 
Filter-paper, folding of . 
Flame, structure of . . 
Flax, rapidity of growth 
Flaxseed, grading of . . 
Fodders, composition of 
cutting of . . 
Food, relation of, to health . 
requirements of animals 
supply and stage of growth 
Foods, caloric value of . . . 

combination and digesti 

bility of .... 
cost and value of . . 
factors influencing diges- 
tibility 320, 361 

influence of cooking upon 

digestibility .... 323 
mechanical condition of, 
and digestion . . . . 3 2 ° 



305 
305 
305 
307 



308 

309 
308 
308 
306 
306 
304 
304 
90 
172 

25 
50 
239 
288 
257-258 
260 
378 
329 
330 
3i3 

321 
359 



3^4 



INDEX 



Foods, palatability of . . . . 3 22 
refuse and waste matters 

of 368 

Formula 12 

Formulas, structural . . . . 178 

Fruits 300-303 

dried 303 

food value 303 

Fuels no 

Galvanized iron 142 

Gasoline, use of 105 

Gelatin 216 

Germination of seeds . . . 225-227 

conditions necessary for . 227 

Glass 131 

tubing, bending .... 22 

cutting .... 21 

Gliadin 260 

Globulins 208 

Glucose, test for 141 

Gluten 260 

meal 296 

Glutenin 261 

Grains, composition of . . . . 290 

cost and value of . . . 343 

grading of 382 

Grapes 302 

Grass, pasture 254 

Gypsum 130 

Helium 67 

Hemoglobin 35 2 

Horses, foods for 33* 

food requirements of . . 331 
Human and animal feeding com- 
pared 356 

body, composition of . 354 

food problems .... 360 

foods, composition of 374-380 

cost and value of 359 

rations 358 

calculation of . . 358 

requisites of . . 363 

Hydrated cellulose 171 

Hydrocarbons 104 

Hydrochloric acid .... 76-80 

preparation . 76 



Hydrochloric acid, properties . 78 

Hydrogen 36-40 

importance .... 39 

occurrence .... 36 
preparation . . . 36-37 

properties 38 

peroxid 67 

sulfid 96 

Hydroxyl 69, 71 

Illuminating gas 106 

Indestructibility of matter . . 5 

Insecticides 145 

Insoluble proteids 211 

Invert sugars 181 

Iron 133 

compounds I33~i37 

galvanized 142 

in plants 161 

ores, reduction 133 

rusting of 137 

wrought . 135 

Keratin 353 

Kerosene oil, testing of ... . 105 

Laboratory manipulation . . 19-30 

practice, important . 19 

Lactose 180 

Law of definite proportion . . 17 

multiple proportion . . 89 

Lead 143 

carbonates 143 

compounds 143, 146 

oxids 143 

uses of 144 

Lecithin 234 

Lemons 301 

Levulose 183 

Ligno-cellulose 172 

Lime kiln . 128 

Lime, slaking of 131 

Limestone 128 

Linseed meal 294 

Magnesium, occurrence . . . 132 

in plants .... 161 

salts 132 



INDEX 



385 



Maintenance ration 328 

Maize, as food 278 

as forage 254 

composition of .... 273 

kernel . . 273 

glutinous and starchy . . 275 

grading of 285 

husk 2\2 

leaves 241 

moisture 277 

products 278 

proteids of 274 

roots 240 

stalk 241 

structure of kernel . . . 273 

varieties of 276 

Malic acid 196 

Malt sprouts 296 

Maltose 180 

Mangels 300 

Marsh gas 104 

Matter, indestructibility of . . 5 

Measuring liquids 24 

Meats, albumin of 352 

albuminoids of ... . 353 
« iposition of . . . 348-355 

digestibility of . . . . 371 

proteins of 330 

Mechanical mixtures .... 7 

Mercury 145 

compounds 155 

Metric equivalents 23 

Mica 100 

Milk solids 152 

sugar 1S0 

Mill and by-products . . . 291-298 

Millet 252, 290 

Mineral food, assimilation of, by 

plants 235 

matter of crops . . 153-168 

oils 107 

in a ration 370 

Minium 143 

Molecular weights 14 

Molecules 5 

Mortar 130 

Mucin 216 

Multiple proportion, law of . . 89 

Myosin 209, 352 

2C 



Naming of acids 71 

bases 71 

sal ts 72, 73 

Neutralization 71, 73 

Nitrates 82 

Nitric acid 82-84 

importance .... 84 
preparation .... 82 
properties .... 83 

Nitrogen 41-44 

assimilation of, by plants 235 
compounds, importance 
of 44, 89 

. 214 

• 4i 
. 86 
41-42 

• 43 



204- 



44 
188 
223 
349 



determination of 
occurrence 
oxids of . . 
preparation 
properties . . 
role in plant and 
mal life . 
Nitrogen-free extract 
Nitrogenous compounds 

matter, animal bodies 
Non-nitrogenous compounds. food 

value 202 

Non-nitrogenous compounds, 

general relationship .... 202 
Note-book, laboratory .... 27 

Nuclein 326 

Nutrients, digestible, of foods . 326 

Nutrition 311-348 

Nutritive ratio 340 

Oat feed 295 

hay 252 

Oats, composition of .... 279 

as food 280 

grading of 286 

structure of kernel . . 279 

Olein 191 

Olives 302 

Oranges 301 

Organic compounds in plants . 1 1 1 

matter 168 

decay of ... 113 

production of . . 236 

Osmosis 229 

Oxalic acid 197 

Oxidation 34 



3 86 



INDEX 



Oxids 33 

Oxygen 30~35 

importance 34 

occurrence 30 

preparation 30 

properties 33 

Ozone 67 

Palmitin 190 

Paris green 145 

Parsnips 300 

Pectin bodies 187 

Pentosans 186 

Peptic ferments 318 

Peptones 210 

Petroleum 104 

Phosphates go 

fertilizers .... 90 

in human foods . . 370 

Phosphoric acid 90 

Phosphorus 89 

compounds .... 91 

importance .... 91 

oxids 89 

in plants 162 

properties .... 89 

Physical change 3 

properties defined . . 9, 10 

Physics 4 

Pigs (see swine). 

Plant ash 153-167 

growth 224-234 

juices, movement of . . 229 

life, chemical change . . 8 

physical change . . 8 

Plaster of Paris 130 

Plumbing 28 

Polariscope 185 

Porcelain 139 

Potassium 121 

carbonate 122 

chlorate 123 

compounds . . . 1 21-123 

hydroxid 121 

nitrate 122 

in plants 158 

sulfate 123 

Potatoes 299 

Pottery 139 



Prairie hay 252 

Properties, chemical .... 10-11 
of elements and com- 
pounds .... 9-18 

physical 9-10 

Proportion, law of definite . . 17 

Proteids 205 

amount in plants . . 213 
chemical properties . . 206 
classification .... 207 
digestibility of . . . 318 
food value . . . .212, 262 

insoluble 211 

of meat 350 

physical properties . . 206 

of wheat 260 

Protein, crude 213 

Proteoses 221 

Protoplasm 231 

Quartz 98 

Radicals 71 

naming of 71 

Rape 254 

Rational feeding of animals . 328-347 

men . . 356, 380 

Rations, balanced . •. . . . 328 

caloric value of . . . 341 

maintenance .... 328 

standard 329 

Reactions 1 15-120 

illustrated .... 11 6-1 17 

impossible 118 

Reagent bottles, handling of . . 25 

Reduction 47 

Rice 281 

Roots 299, 300 

Rye 280 

grading of 287 

Salts 69 

acid 72 

double 72 

naming of 72, 73 

Sand culture 157 

Sanitary conditions and feeding 344 

Saponification 191 

Seeds 224-229 



INDEX 



387 



Seeds, and crop growth .... 245 

ash of 224 

nitrogenous compounds of . 225 

Sheep, food requirements of . . 338 

Silage 256 

Silica 98 

Silicates 100 

Silicic acid 98 

Silicon 98 

compounds, importance of 100 

Silo, losses in 256 

Sodium 123 

carbonate 125 

chlorid 124 

hydroxid 125 

nitrate 124 

phosphate 126 

in animals 348 

in plants 159 

salts 122-127 

Soils 100 

Spontaneous combustion ... 50 

Starch 173-179 

chemical properties . . . 175 

food value 176 

function 176 

physical properties . . . 173 

in seeds 226 

Stearin 190 

Steel 135 

Steer-feeding 330-334. 

Stover 254 

Straw 250 

Strawberries 301 

Sucrose 180 

chemical properties . . 180 

physical properties . . 180 

Sugar 179-187 

beets 185 

Sulfates 95 

Sulfids 96 

Sulfur 92 

dioxid 93 

preparation 92 

properties 92 

uses 93 

in plants 163 

Sulfuric acid 93 

properties .... 94 



Swine, food requirements of . . 336 

Symbols n 

Syntonin 210, 352 

Tartaric acid 196 

Timothy hay 251 

Tin 143 

salts 143 

Trypsin 318 

Tubing, glass, bending .... 22 

cutting .... 21 

Turpentine 107 

Typhoid bacillus 57 

Valence 17 

table of 12 

Vegetable foods 379, 380 

digestibility of . 372 
Ventilation of rooms . . . 64-66 

Water 54 _ 62 

borne diseases 57 

contamination of . . . 56, 60 

culture 156 

of crystallization .... 56 
distillation of .... . 62 

electrolysis 54 

filters 60, 61 

mineral matter of . . . 60 

natural 56 

organic matter in ... 57 

oven 149 

physical properties ... 58 

in plants 151 

purification of ... 61, 62 

Waxes 192 

Weighing 23, 152 

Weights, atomic 14 

molecular 14 

Wheat 259-272 

American and foreign . . 272 
as animal food . . . . 270 
as human food . . . . 271 

bran 291 

bread-making properties of 261 

by-products 291 

composition of varieties . 269 

feed 294 

flour, grades of ... . 268 



3 88 



INDEX 



Wheat, germ 268 

gluten of 261 

grading of 283 

influence of climate upon . 263 

fertilizers upon 264 

middlings 293 

nitrogen content of, and 

flour 263 

proteids of 260 

rapidity of growth . . . 235 

screenings 294 



Wheat, shorts 293 

storage of 267 

structure of kernel . . . 259 

unsound 268 

variations in composition . 265 

White lead 144 

Zeolites 100 

Zinc compounds 142 

occurrence 142 



'T^HE following pages contain advertisements of a 
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and on related subjects. 



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Professor of Agricultural Chemistry, University of Minnesota, and 
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Wool, Cotton, and Rubber ; The Soil ; Commercial Fer- 
tilizers ; Farm Manures ; The Animal and Its Feed ; 
Human and Animal Foods; Milk and Its Products; 
Poisons for Farm and Orchard Pests. 



THE MACMILLAN COMPANY 

Publishers 64-66 Fifth Avenue New York 



Exercises in Elementary 

Quantitative Chemical Analysis 

for Students of Agriculture 

By AZARIAH THOMAS LINCOLN, Ph.D. 

Assistant Professor of Chemistry, University of Illinois 
AND 

JAMES HENRY WALTON, Jr., Ph.D. 

Assistant Professor of Chemistry, University of Wisconsin 
New York, 1907. Third Reprint, 1910. Cloth, 8vo, 218 pages, $/.jo net 

This book is the outgrowth of several years' 
experience in teaching Quantitative Analysis to 
students specializing in Agriculture, Chemistry, 
Medicine, and Household Science. No attempt 
has been made to present a complete treatise on 
Quantitative Analysis ; but a few typical exercises 
have been chosen to illustrate the fundamental 
principles of the most important methods of 
manipulation. 

Owing to the importance of calculating the 
amount of various elements in substances analyzed, 
a special part of the book (Part V) deals with this 
subject (Stoichiometry). A large number of prob- 
lems have been here introduced for the sake of 
practice. 

THE MACMILLAN COMPANY 

Publishers 64-66 Fifth Avenue New York 



iEP 5 1913 



